Mills, C. K. The Physiological Areas and Centers of the Cerebral Cortex of Man, with New Diagrammatic Schemes. Univ. of Penna. Medical Bulletin, XVII, 3, pp. 90-98, May, 1904.

The history and theory of cortical localization are briefly reviewed and the new features of the author's diagrams commented upon. C. J. H.

McCarthy, D. J. The Formation of Bone Tissue within the Brain Substance. A Contribution to the Inclusion Theory of Tumor Formation. Univ. of Penna. Medical Bulletin, XVII, 3, pp. 120-121, May, 1904. Report of a small tumor containing true bone tissue which appeared in the cerebral hemisphere of a young cat subsequent to an experimental lesion.

C. J. H.

Piper, H. Das elektromotorische Verhalten der Retina bei Eledone moschata.

Archiv für Anatomie und Physiologie, pp. 453-474, 1904.

The author starts out from the observation that water, and especially the water of the Mediterranean Ocean, strongly absorbs red and yellow rays of light so that the sunlight which reaches moderate depths below the surface is strongly tinged with blue and green. HIMSTEDT and NAGEL had discovered in 1901 that the action currents of the frog's retina are stronger for intense yellow light (natrium) than for any other intense colored stimulations which they applied. Now the yellow portion of the solar spectrum as measured bolometrically has a greater energy than any other part, so that these authors referred the greater action currents for yellow light to an economical adaptation of nature, whereby the light most predominant in nature has also the greatest stimulation value. The human eye receives the most intense sensation from the yellow part of the spectrum, so that they further concluded that the action currents of the retina are a fair measure of the intensity of the sensation being carried to the brain. And in confirmation of this they actually discovered that a frog's retina when adapted to "rod vision" before being removed, would then give greater action currents for blue-yellow light than for the yellow light to which the unadapted retina best responds; just as the human adapted eye sees the blue-yellow part of the spectrum as brightest (PURKINJE phenomenon).

Now Dr. PIPER inquires whether animals living some distance below the level of the sea will give the strongest retinal action currents for that color of light to which they are most exposed; and more particularly, whether animals living in the depths of the Mediterranean Ocean will have the strongest retinal currents for that blue light by which they are always surrounded. In fact, the author finds this to

be the case with the Cephalopod Eledone moschata. He demonstrates this admirably by tables and curves. Whereas the action currents of the frog's retina, for he was careful himself to repeat the experiments of HIMSTEDT and NAGEL, are the greatest for spectral light of about 590 μμ wave-length (yellow), those of the cephalopod's retina are greatest around the wave-length 500 μu (blue-green). For considerably weaker intensities of light the frog's retina gave the strongest currents for the wave-length 560 μu (yellow-green); that is, when the retina was more less adapted to, darkness the position of maximum currents shifted from the yellow toward the yellow-green. This is in precise agreement with HIMSTEDT and NAGEL.

For both animals the author used a dispersion spectrum from the NERNST lamp; and he bases his conclusions on experiments with 13 specimens of E. moschata. In view of the extreme similarity of the results from the several individuals, this number seems quite sufficient to establish the author's point. The author used this species alone, because it was the only one which could be easily obtained and of which the eye on being removed retains vitality enough to make experimentation possible. It is interesting to note that the action current both attains its maximum and subsides very rapidly. Dr. PIPER does not confirm the results of BECK as regards the direction of the action current.

The paper is written with exemplary clearness and conciseness, and cannot fail to convince the careful reader; and this the more in view of the rare and delightful modesty with which the author claims to have established his interesting and important point.

E. B. H.

Keeble, Frederick, and Gamble, F. W. The Color-Physiology of Higher Crustacea. Phil. Trans. Roy. Soc. London, Ser. B, Vol. 196, pp. 295-388, 1904.

Notwithstanding the fact that color patterns and color changes have always interested naturalists greatly, and that much has been written concerning "protective" coloration and "color mimicry," it is only recently that color phenomena in animals have been subjected to any very close and accurate scientific investigation, looking toward an explanation of their origin. The work of STEINACH, RABL and CHUN on mollusks, and of KEEBLE and GAMBLE on Crustacea not only clears up many points that were uncertain before, but will also doubtless stimulate to further investigation in a field of inquiry that promises to be most fruitful.

The present monograph by KEEBLE and GAMBLE is one which de

lights the eye by the excellence of its form and arrangement, and rejoices the heart with the thoroughness and accuracy of the work and the far-reaching importance of its results. It is really a continuation and amplification of the investigation by the same authors on "Hippolyte varians a study in color-change", extending the observations made on this species and including a study of Crangon, Palaemon, Carcinus, Portunus and Galathea, based upon Macromysis as a fundamental type.

In Macromysis the authors observe that the color units, the chromatophores, are arranged in three main groups and one accessory group. The three main groups are (1) the neural, in relation to the brain and nerve-cord; (2) the visceral, connected with the alimentary tract, liver and gonad; (3) the caudal group on the upper surface of the tail. These three groups are so related that they may be conceived as forming a system, the primary system of chromatophores. The accessory group, on the other hand, is related to outlying structures, and may be considered as an incipient accessory system. The chromatophores are not simple cells, as they are widely considered, but consist of a protoplasmic, pigmented center, enclosed in a spherical thin-walled bag, which is pierced by the proximal ends of a number of cells varying from five to nine. These cells have their nuclei in, or close to, the chromatophore center, and extend outward in branched, fibrillated processes, the whole being not unlike the branching of a tree. Some of these branches are 2 mm. and over in length.

The chromatophore centers of Macromysis contain two kinds of pigments, a brown pigment, which turns red and is finally decolorized under the influence of oxydizing agents, and a small quantity of pigment which is bright yellow or white by reflected light, but has a grayish color in transmitted light. It is the brown pigment that gives the characteristic color pattern to the animals, giving them a dark brown tint when expanded, i. e., when the pigment migrates to the branches, and leaving them colorless or gray when the pigment contracts to the

center.

In decapod Crustacea the situation is much more complex. The color-marking of the adult decapod is determined by the development of the secondary system of chromatophores, which completely covers up the first and differs from it in having much shorter branchings and being much more decentralized. In the larval stages, however, through the Mysis stage, the primary system remains in the ascend1 Keeble, Frederick, and Gamble, F. W. Hippolyte varians: a Study in Color-change. Quart. Journ. Micros. Science, Vol. 43, pp. 589-698, 1900.

ency, so that the larva is more like Macromysis than it is like the adult This primary system persists unchanged in the adult but is overlaid by a secondary, and sometimes even by a tertiary, system of chromatophores. The pigments of this secondary system are either absorbing or reflecting; the former, red, yellow, brown, violet and diffuse blue, are the same in transmitted and reflected light, the latter are only effective in reflected light, and appear white, yellow, greenish or blue, as the case may be.

The question is raised whether these chromatophore systems and the color patterns resulting from them are inherited or acquired. After marshalling the evidence the authors conclude that the primary system, owing to its appearance in the earliest larval stages, and its persistence in the adult, is inherited in all cases. In Crangon and Palaemon there is a steady, constant development of the secondary pattern from the embryo to the adult, and hence the secondary system is thought to be inherited in these forms. In Hippolyte, however, there does not seem to be any such constancy of development, but the dominant color-pattern is rather a result of the action of the environment.

Regarding the mechanism of pigment migration the authors hesitate to express themselves. They are not inclined, however, to accept POCHET'S view that it is due to the active amoeboid movement of cell processes, but prefer to account for it by the turgidity of the constituent cells of the centers, caused chiefly by the action of light, and controlled to a greater or less extent by the nervous system. This view is strengthened by the fact that in old Mysids "the pigment at times bursts the frondose extremities of the chromatophores and exudes into the surrounding tissues." Moreover, the origin of the chromatophores is to be found, not in connective, but in glandular tissue, and their action seems to be like that of a gland, continually secreting or transforming pigment substances.

In Hippolyte varians there is a regular alternation of the diurnal color-pattern, due to red and yellow pigments, with the nocturnal, which is blue. Under appropriate light stimulation the red and yellow pigments flow out through the branches, and when the stimulation. is withdrawn, these pigments contract and there is a diffusion of blue. The authors think, however, that the blue pigment does not serve any protective purpose, but is rather a by-product obtained by the transformation of the yellow and red pigments, and "exudes from the chromatophores, permeates the tissues and subsequently disappears."

Perhaps the most interesting portion of the paper is the last section, which deals with the influence of light on littoral Crustacea.

During the day Palaemon and Hippolyte are quiet and sluggish, but in the evening they become very active and restless, many throwing themselves out of the shallow pans in which they are kept. Hence the authors think that these animals should be considered nocturnal. Experiments on phototropic reactions (going toward or away from the light) showed that the animals experimented on formed a series, Palacmon being negatively phototropic (light-shunning), Hippolyte positive (light-seeking), and Macromysis negative on a white ground but positive on a black ground. The zoeae of Palaemon, however, are positive, and if given a choice of ground select the white. The adult Palaemon and Macromysis choose the black, while Hippolyte in all stages prefers the white. A test was made to determine whether the positively thigmotropie Palaemon could be driven from the bottom of a bottle, whose upper portion was darkened, by its negative phototropism. As long as there was nothing in the upper part of the bottle to cling to, the animal returned to the bottom after a short swim above. When an inclined stick was placed in the upper end of the bottle, Palaemon remained clinging to it in the shadow.

The effect of light upon pigment migration is discussed in great detail. The effect of light stimulation was found to be in part direct. and in part indirect, i. e. through the eyes and the nervous system. The indirect response is the most important for color display, but its action is slower, so that the direct response often gets a start, and then is checked by the indirect. The direct response is determined not by the background but by the incident light, whereas the indirect response is determined by the background entirely, a white ground causing contraction of pigments, and a black ground expansion. "There is a close agreement between the phototropic reaction and the pigmentmovement reaction; both depend on the eye and both are determined by background".

"A monochromatic light in conjunction with a scattering (white) or absorbing (black) background, produces the same ultimate effect on pigment movement as does a white light in conjunction with the same background. The fact of background must be taken into consideration in all experiments on phototropism."

In conclusion let it be said that the work is well supplied with summaries, an appendix of 17 tables, a bibliography of 62 numbers and seven splendid plates.

J. CARLETON BELL.