396). The morphological objections are still more serious. In the first place, the structure of the olfactory epithelium is totally unlike that of the organs of the auditory and lateral line systems, where hair cells extending only part way through the epithelium are always present. The methods of stimulation of the two sets of organs are totally different and it is not easy to see how one could have been derived from the other. And finally, all of the acustico-lateralis nerves terminate in the brain in a single center with very characteristic connections, which are totally unlike those of the far distant olfactory

center.

At the close of the discussion of the cranial nerves we find this excellent passage: "From what has been said above it is clear that the usual arrangement of the cranial nerves in twelve pairs does not represent their true relationships with one another. The various pairs are serially homologous neither with one another nor with the typical spinal nerves, nor can they be regarded as representing twelve cranial segments. Indeed, it would seem that comparatively little information with regard to the number of myotomic segments which have fused together to form the head is to be derived from the cranial nerves."

On page 458 we read, " 'Nothing is yet known concerning the development of the various forms of tactile organs," the author having apparently overlooked the papers by SZYMONOWICZ in the Archiv f. mikr. Anatomie, 1895 and 1896.

The adverse criticisms above are, however, relatively insignificant as compared with the general excellence of the discussion as a whole, which is clear and philosophical in design and treatment.

1

Motor Nerve Termini in Insects. 1

C. J. H.

The motor nerve terminations in the striated muscles of insects have been studied by various methods by many histologists, among whom may be mentioned Rouget, Ranvier, FOETTINGER, V. THANHOFFER, CIACCIO, BIEDERMANN, RAMON Y CAJAL and R. MONTI. These investigators have disagreed in many points, but the author di vides them into two main classes. The first class includes those, who, like RANVIER, recognize in the striated muscles of insects, as in those of the higher animals, a DOYÈRE'S elevation consisting of granular protoplasmic substance containing more or less numerous nuclei. The nerve fiber, when it reaches this elevation, loses its sheaths, the neuri

1 Sulla terminazione nervosa motrice nei muscoli striati degli insetti. Preliminary note by ALBERTO AGGAZZOTTI,

lemma becoming continuous with the sarcolemma, and breaks up into fibrils which pass into the granular substance but do not pass beyond it to enter into relation with the contractile substance of the fiber. The second class is represented by FOETTINGER, who also recognizes a DOYÈRE'S elevation under the sarcolemma, containing numerous nuclei. The terminal branches of the nerve fiber, however, according to FoETTINGER, pass through the granular substance and out in different directions, finally fusing with the isotropic or intermediary disk of the muscle fiber. This, then, represents the theory that there is a direct anatomic continuity between the nerve fiber and the muscle fiber.

The author's investigations were made on Hydrophilus piceus and Melolonta vulgaris. He used the haematoxylin method suggested by Dr. C. NEGRO in 1889. The fresh muscles of the wings and legs of the living insects were immersed for 24 to 48 hours in DELAFIELD'S haematoxylin solution, washed thoroughly in water, decolorized in a weak acid mixture of glycerine, water and hydrochloric acid. They were then teased and mounted in a medium consisting of equal parts of glycerine and

water.

In the insects studied, the motor nerve undergoes dichotomous division of the axis cylinder, the two branches diverging and entering a mass of granular substance which has in profile the form of a cone slightly elevated above the level of the muscle fiber. In the interior of the granular substance, which is stained more or less intensely violet, he finds three or four nuclei which appear granular and stain deeply, resembling the telolemma nuclei described by KÜHNE in the motor plaques of vertebrates. He was unable however to find the so-called sole-nuclei also described by KÜHNE.

While the author has, by this method, confirmed the findings of other investigators regarding the existence of a DOYÈRE'S elevation of granular substance containing nuclei, similar to those found in vertebrates, he has as yet been unable to establish several of the most important points in dispute as to the structure of the motor ending in the striated muscles of insects. He has been unable to determine whether the cone-shaped eminence described by him is under the sarcolemma or not and he is not certain from his preparations that the nerve fibrils form in the granular substance a terminal arborization similar to that found in the motor endings in the striated muscles of vertebrates. These points, with the minuter structure of the DOYÈRE'S elevation, he reserves for further investigation.

The main interest of the research seems to have centered in the question whether the fibrils end in the DOYÈRE's elevation or pass be

yond it in a manner similar to that of the ultra-terminal fibers described by RUFFINI. In the twelve preparations described and figured by the author, eight show one or more fine nerve fibrils separating themselves from the main fiber either just before it enters the granular substance or just after it leaves it. These secondary fibrils pass on for variable distances to end either on the same or on a contiguous muscle fiber. He therefore concludes that the motor nerve in the striated muscle of insects does not as a rule end in the DoYÈRE'S elevation, but in the majority of cases passes beyond this, subdividing into a number of fibrillae, which end in other eminences of granular matter either in the same or in one of the neighboring muscle fibers.

While the author has neither, with RANVIER, established the presence of a terminal arborization in the granular sole-plate of the striated muscles of insects, nor, with FOETTINGER, determined a direct anatomic relation between the nerve fiber and the striae of the muscle fiber, he seems, if I interpret his figures and descriptions correctly, to be inclined to favor the view of the latter that the ultra-terminal fibrils, at least, are often closely related to the striae of the muscle fiber. The structure of the motor ending seems, however, from the figures given, to resemble in many respects that of the terminal motor plaques found in the striated muscles of vertebrates and it seems probable that a further study of these endings by some method which more completely stains the terminal nerve fibrils and more perfectly differentiates the nerve and muscle tissues will show a still greater correspondence.

DR. LYDIA M. DEWITT.

The Comparative Anatomy of the Brains of Lemurs and Other Mammals.1 Professor ELLIOT SMITH explains in his introduction that this investigation was undertaken primarily to consider the possibility of homologizing the sulci of the cerebral hemisphere in different orders of mammals; but on account of the mass of the material to be considered he has found it necessary to limit this report in two ways, (1) by confining attention to two sulci, the only two which are absolutely constant in all Primates; viz., the calcarine and Sylvian; and (2) by restricting the detailed account of the sulci to the lemurs with, however, extensive comparisons with other mammalian orders.

This account fills 112 pages and is illustrated by 66 text-figures drawn with the beautifully clear, bold outlines characteristic of the

1 SMITH, G. ELLIOT. On the Morphology of the Brain in the Mammalia, with Special Reference to that of the Lemurs, Recent and Extinct. Trans. Linnean Soc. of London, 2 Ser., VIII, Part 10, 1903.

previous contributions by this author. The more important of the conclusions reached are included, along with others, in the extract from the catalogue of the museum of the Royal College of Surgeons given above, and need not be summarized here, save to add one point: "The features of the Prosimian brain become really intelligible only on the supposition that the Lemurs have advanced a considerable distance in the main stream of the evolution of the Primates and have then retrograded; among other manifestations of this retrogressive process many interesting phases of the disintegration of the cerebral sulci are exhibited, so that it becomes possible to recognize the constituent elements of many compound sulci in the Primates, and so the more readily to compare them with the furrows found in other mammals."

C. J. H.

Development of Lepidosiren.'

This contribution treats of the general epidermis, buccal cavity, hypophysis, central nervous system and sense organs, and is illustrated by four excellent plates. Notable among the figures are drawings of the brain from different aspects at successive stages, showing also the roots of the cranial nerves. Typical fourth and sixth nerves were found and figured for the first time.

The brain of the adult Lepidosiren closely resembles that of Protopterus. The thalamencephalon and mesencephalon do not become marked off from one another until relatively late and the cerebral hemispheres arise as two separate lateral bulgings of the wall of the thalamencephalon. The most distinctive feature of the contribution is concerned with the histogenesis of the motor nerves, of which we are promised a more full description later. The motor nerve trunks are already laid down at a period when myotom and neural tube are still in close apposition. As development proceeds and the myotom recedes from the spinal cord the nerve trunk lengthens out, increases in thickness, and becomes ensheathed in mesenchymatous protoplasm. At the earliest stage observed the protoplasm of the nerve trunk is continuous with that of the myotom cells, which are provided with tail-like processes extending into the nerve.

C. J. H.

1KERR, J. GRAHAM. The Development of Lepidosiren paradoxa. Part IIIDevelopment of the Skin and its Derivatives Quart. Journ. Micr. Sci., N. S.,

vol. XLVI, 1902.