sects in question are Halobates and Halobatodes. . . . They feed upon the floating bodies of dead marine animals, and may be seen to run out from such objects when alarmed by the approach of a boat. These insects belong to the Rhynchota (Hemiptera) and in some respects come pretty near to such forms as Hydrometra or Velia." Walker has found once or twice several specimens of marine Hemiptera belonging to the group Halobates, gathered round floating pieces of seaweed, as if obtaining. nutriment. However, it must be acknowledged, that practically nothing is known about the food of these creatures. McCook has demonstrated that individuals of Gerris remigis feed readily on the juice "of finely ground boiled beef." They take such food, with avidity, even in their own habitat.

If a more critical study should be made of the food of aquatic bugs in general, in their various habitats, I believe that still further evidence would be accumulated, showing that considerable food, of the other kinds, besides insects, was used by these interesting forms. In fact Hungerfords himself has pointed out a number of exceptions, some of which I can substantiate from my own observations, and to which I can add others also from my own observations.

The following statements agree with those of Hungerford to the extent that the aquatic bugs now to be mentioned, are not entirely predatory, nor is their food entirely that of insects: I have found by microscopic examination of the alimentary system that water-boatmen of the genus Arctocorisa feed on vegetable matter; diatoms and Oscillatoria have been identified. They probably obtain most of this from the ooze on the surface of the mud, at the bottom of the pond or stream. In order to obtain additional evidence, I placed some of

5 Ibid., pp. 380-381.

6"On the Genus Halobates Esch., and Other Marine Hemiptera," Entomologist's Monthly Magazine, Second Series, Vol. IV., p. 231, 1893.

7''Nature's Craftsmen," New York, 1907, pp. 363-365.

8 Loc. cit., pp. 336-337.

9 Ibid.

the water-boatmen in shallow, glass dishes of water, with some of the ooze containing algal débris, as suggested by Hungerford,10 but my observations were discontinued before I was satisfied definitely that these bugs scooped up this substance with their front legs, and used it as food. I also placed back-swimmers of the genus Notonecta in shallow, glass dishes of water and fed them with small crustaceans, such as copepods and ostrocods. The backswimmers appeared to thrive on this food. By means of a similar experiment, I was able to demonstrate that the marsh-treader, Hydrometra martini, will feed on copepods tangled in the surface-film. This was more likely to occur when the water became somewhat stale.

It is well known that many members of the family Gerridæ, which consists of an assemblage of aquatic Hemiptera living on the waterfilm, feed mainly on terrestrial insects which fall into the water and float on its surface. Water-striders are considered to be entirely predatory in their manner of feeding, and so far as I know there is no statement to the contrary in the literature on aquatic Hemiptera. However, it may be of interest to state that I have definite proof that Gerris remigis and Gerris marginatus both feed, at times, on vegetable matter. The following statement is a modified extract, taken from my field notes: After having studied water-striders in their natural habitats for several months, especially with reference to their food relations, I decided that both Gerris remigis and Gerris marginatus were entirely flesh-eating. However, on October 14, 1911, this opinion was changed. At the time, I was making observations of the water-striders on the surface-film of a brook near Whiteheath, which is approximately eighteen miles southwest of Urbana. Small red fruits were observed, drifting downstream, and these attracted the attention of the water

striders at once. Both species seized them readily, Gerris remigis with the greater avidity, and pushed their beak-like mouth-parts through the outer skin, down into the inner fruit. Some of the fruits, with their attendant water-striders, drifted near the bank of the

10 Loc. cit., p. 337.

stream, and with the aid of a large readingglass attached to a pole, it was possible to see the feeding movements of the mouth-parts. Several observations were recorded later than this of specimens of Gerris remigis sucking the juices of these berries. Only on one other occasion was Gerris marginatus seen to use this fruit as food. The plant from which these fruits came is commonly known as the coralberry or Indian currant, Symphoricarpos vulgaris. It is very common along the banks of the brook near Whiteheath.

I have found that, during my observations of the food habits of water-striders in captivity, while confined in aquaria, both species mentioned suck the juices of freshly killed Physa and Planorbis. They also feed on fresh beef, on the soft parts of banana fruit, and on the inner, softer parts of the skin.

These observations seem to add additional evidence to Hungerford's11 contention that aquatic Hemiptera are neither entirely predacious, nor do they feed entirely upon insects. It is very likely that other observers could report further observations of the character that have been recorded here.

C. F. CURTIS RILEY THE NEW YORK STATE COLLEGE OF FORESTRY, AT SYRACUSE UNIVERSITY, SYRACUSE, NEW YORK

SCIENTIFIC BOOKS

Wild Animals of North America: Intimate Studies of Big and Little Creatures of the Mammal Kingdom. By EDWARD W. NELSON. Natural-Color Portraits from Paintings by LOUIS AGASSIZ FUERTES. Track Sketches by ERNEST THOMPSON SETON. Published by the National Geographic Society, Washington, D. C., U. S. A.; 8vo, pp. +385-612, folded frontispiece, 108 colored illustrations on text paper (not plates), 85 halftone illustrations. [This is essentially a reprint of two articles which appeared in the National Geographic Magazine, for November, 1916, and May, 1918. The changes comprise repaging beyond page 472, the readjustment of the 11 Loc. cit., pp. 336-337.

matter on pages 473-475, the replacement of a half-tone on page 475, the rectification of page references to illustrations to accord with the new paging where needed, and readjustment of the matter from page 571 on, so as to admit 32 new illustrations of footprints and the captions to these.]

This is a work which meets to a gratifying degree the need for an essentially non-technical treatise upon the natural history of the mammals of North America. No living person is better equipped to carry to a successful conclusion such an undertaking than is its author. Nelson has contributed in the field of vertebrate zoology now for over forty years, to be explicit, beginning in July, 1876 (Bulletin Nuttall Ornithological Club, Vol. 1, p. 39). With a background of long experience in the field, and with further years of official connection with the United States Biological Survey and its unique resources in mammalogy, he has made available a brochure of pleasing amplitude and satisfying authoritativeness.

Between the colored pictures and the written sketches the public can gain from this contribution a better idea of our principal mammals than from any other available publication. It should awaken a generally greater interest in our native mammals, and this will help build up a desire for the conservation of the harmless and useful species such as has resulted from the public education in relation to our bird life. On the other hand it is important to be able to distinguish those mammals, chiefly of the order Rodentia, which are thoroughly inimical to human interests. People at large must know how to cope with these enemies. It would seem that a full knowledge of the natural history of such animals is essential to determining the most successful means of controlling them and to applying these means properly to the varying conditions throughout the country. Nelson's accounts of our injurious mammals are full of stimulative suggestions along these lines, and while the work as a whole can not be considered as an "economic" publication, its influence will go far to secure adequate popular consideration of these matters.

The species are taken up in groups, in so far as this can be done safely. Each biography, of which there are 119, is, as a rule, a composite applying to a number of near-related forms, thus simplifying matters of presentation, and avoiding repetition. A marked feature of the book is the degree of concentration attained; there is no trace of padding, and no room for baseless speculation, sentimentalizing or humanizing, such as characterize many current "nature" books. At the same time the style is animated and thoroughly entertaining, a gift of composition which Nelson has exercised in many preceding contributions. Here is an instance, unfortunately a rare one, in which a man who really knows the field has put out a popular book on a natural history subject.

Many are the portrayals which are evidently based on Nelson's own personal field knowledge, some of them involving facts here for the first time made known to science. His account of the behavior of kangaroo rats in Lower California is particularly apt in illustration of the above statement.

During several nights I passed hours watching at close range the habits of these curious animals. As I sat quietly on a mess box in their midst. . . [they] would forage all about with swift gliding movements, repeatedly running across my bare feet. Any sudden movement startled them and all would dart away for a moment, but quickly return. . . . They were so intent on the food [grains of rice put out for them] that at times I had no difficulty in reaching slowly down and closing my hand over their backs. I did this dozens of times, and after a slight struggle they always became quiet until again placed on the ground, when they at once renewed their search for food as though no interruption had occurred. . . . While occupied in this rivalry for food they became surprisingly pugnacious. If one was working at the rice pile and another rat or a pocket mouse approached, it immediately darted at the intruder and drove it away. The mode of attack was to rush at an intruder and, leaping upon its back, give a vigorous downward kick with its strong hind feet. Sometimes an intruder, bolder than the others, would run only two or three yards and then suddenly turn and face the pursuer, sitting up on its hind feet like a little kangaroo. The pursuer at

once assumed the same nearly upright position, with its fore feet close to its breast. Both would then begin to hop about watching for an opening. Suddenly one would leap at the other, striking with its hind feet, . . . [producing] a distinct little thump and the victim rolled over on the ground. After receiving two or three kicks the weaker of the combatants would run away. The thump made by the kick when they were fighting solved the mystery which had covered this sound heard repeatedly during my nights at this camp.

The brilliantly coated paper used throughout this book although hard on sensitive eyes, is necessary to the handling of the halftone illustrations. The printing of both the colored and uncolored pictures in all the copies we have seen has been done with pronounced success. The color drawings by Fuertes are admirable and we are astonished at the success with which this noted bird artist was able to turn to mammals, the drawings of which in this contribution mark as far as we know his first efforts in the new field.

A critical reviewer might succeed in finding a number of small points to elaborate upon and of which to complain. For instance: It is trite to say that an Alaska brown bear is no more an animal than is a house fly. Yet here we have the title, "Wild Animals of North America," though there is an evident effort made in the subtitle to remedy the matter by using the expression, "mammal kingdom." But here a taxonomic blunder is tumbled into! We can hardly believe that Nelson himself had anything final to say with regard to the title page of this book, but that the editor of the National Geographic Magazine got in his work here in the belief so characteristic of editors of popular magazines that their public must be talked down to.

But to pin the attention of the reader of this review upon such really minute defects would do violence to the facts in the case, which are that, according to the convictions of the reviewer, Nelson's "Wild Animals of North America" is more uniformly accurate and at the same time replete with information along many lines than any preceding book on American mammals. And even more, it may be declared with confidence that this book is

by far the most important contribution of a non-systematic nature that has appeared in its field in America.

JOSEPH GRINNELL

MUSEUM OF VERTEBRATE ZOOLOGY,

UNIVERSITY OF CALIFORNIA

SPECIAL ARTICLES

THE SUBSTITUTION OF SACCHARIN FOR

SUGAR

IF saccharin can be substituted for sugar it is evident that it must fulfill the functions of sugar and at the same time not produce harmful effects. As a sweetening agent, to be oxidized thereby furnishing energy and to increase oxidation in the body are three functions of sugar. It would seem that saccharin should fulfill admirably the function of sugar as a sweetening agent since it is about 500 times sweeter than sugar. There are some who think that the use of saccharin as a sweetening agent is harmful. The extensive investigations of Herter and Folin1 for the referee board on the effect of saccharin on the nutrition and health of man show that the amount of saccharin that would ordinarily be used has no deleterious effect. Herter found, in fact, that such enormous doses as 4 grams of saccharin per kilogram of body weight could be given to rabbits without injury. It is recognized that saccharin can not fulfill the second function of sugar named, for it is not oxidized to give rise to energy, but passes through the body almost quantitatively unchanged. The object of the present investigation was to determine if it could fulfill the third function of sugar named, that is, does the ingestion of saccharin increase oxidation in the body. We had already found that the ingestion of sugar, as well as the ingestion of the other food materials, produced an increase in catalase, an enzyme possessing the property of liberating oxygen from hydrogen peroxide, parallel with the increase produced in oxidation, by stimulating the digestive glands, par1 Herter and Folin, United States Department of Agriculture, Report 94, 1911.

2 Burge and Neill, The American Journal of Physiology, Vol. 47, No. 1.

results a corresponding decrease in catalase. Stated more specifically, the present investigation was begun to determine if the ingestion of saccharin would produce an increase in catalase, and hence an increase in oxidation in the body just as sugar and the other food materials do.

The animals used were dogs. The sugar used was dextrose, and the saccharin "soluble saccharin," prepared by the addition of a solution of sodium carbonate to saccharin. The amounts of these substances used were 4 grams per kilogram of body weight of the animal. They were introduced into the stomach of the animal by means of a stomach tube. Determinations of the catalase of the blood from the jugular vein were made before as well as at thirty minute intervals after the introduction of the materials. The determinations of catalase were made by the addition of 0.5 c.c. of blood to 50 c.c. of hydrogen peroxide in a bottle at approximately 32° C., and the amount of oxygen gas liberated in ten minutes was taken as a measure of the amount of catalase in the 0.5 c.c. of blood.

The curve marked "sugar" in Fig. 1, was constructed from data obtained before, as well as at thirty minute intervals after, the introduction into the stomach of a dog of 4 grams of dextrose per kilogram of body weight of the animal. It may be seen that the sugar produced 8 per cent. increase in catalase during the first 30-minute interval; 14 per cent. increase during the 60-minute interval; and 16, 14 and 15 per cent. increase during the succeeding intervals. Two days later, five grams of "soluble saccharin" per kilogram of body weight were introduced into the stomach of the same dog. The curve marked "saccharin " in Fig. 1, shows the results. It may be seen that the introduction of the "soluble saccharin" increased the catalase of the blood 3 per cent. during the first 30-minute interval; 10 per cent. during the 60-minute interval; 30 per cent. in 90 minutes; 54 per cent. in 120 minutes, and 56 per cent. in 150 minutes. By comparing the effect of the sugar and of the saccharin on the production of catalase, it may be seen that the saccharin produced a

much more extensive increase in catalase than did the sugar.

The conclusion is drawn that in addition to being a sweetening agent, saccharin, although not oxidized itself, serves to facilitate the oxidation of the other food materials by stimulating the liver to an increased output of catalase, the enzyme in the body principally responsible for oxidation. Hence, it would seem that saccharin should be positively helpful in the diet, instead of harmful, as some have claimed, particularly in a disease such as diabetes where the principal trouble is defective oxidation. W. E. BURGE

PHYSIOLOGICAL LABORATORY OF THE
UNIVERSITY OF ILLINOIS

THE AMERICAN ASTRONOMICAL

SOCIETY

THE twenty-second meeting of the society was held August 20 to 22, 1918, at the Harvard Observatory. Before the gathering it had been expected by many that war conditions would make the attendance so small that it would be scarcely worth while to hold the sessions. As might have been anticipated, however, the number of members of the society residing near Cambridge, together with the staff of the observatory, would make a respectably sized company at any time, and these with the few who were able to attend from a distance made a number which was well up to the average of previous meetings of the society. Although many astronomers about the country are actively engaged in war work, the number of papers presented showed no tendency to decrease, in fact there were the greatest number of communications ever presented at a meeting of the society. This was due primarily to two astronomical occurrences which were not affected by the war, the solar eclipse of June 8, and the appearance of the new star, in Aquila. Each of these events was the occasion of about a dozen papers.

In welcoming the society in his double capacity as host and president, Professor Pickering referred to the last previous meetings at Harvard in 1910, when so many foreign astronomers were present, and he expressed the hope that it would not be too long before similar international meetings of men of science could be held again.

In the intervals between sessions the members were afforded the opportunity to inspect the instruments and work of the Harvard Observatory,