ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
291 
details of the development of Amia , and states that a larva 3 cm. long 
had on the whole the appearance of an adult Amia in miniature. He 
found that in Lepidosteus the first ganoid scale appeared in forms 10 cm. 
long. The author appears to have made a good collection of materials 
for a complete monograph. 
Gills of Ceratodus Embryos.*- — Dr. R. Semon reasserts his obser- 
vation that there is no hint of external (or larval) gills in Ceratodus- 
embryos, since Herr P. Clemens has interpreted one of his figures so as 
to suggest the presence of these organs. 
Spermatogenesis of Selachians.! — M. A. Sabatier continues his 
remarks on this subject. J He finds that in all cases there is a formation 
of primitive nests of germs under the form of a plasmodium, and due to 
the amitotic multiplication of the nuclei of the connective germinal 
tissue. Secondary nests are formed by the amitotic multiplication of 
the nuclei of the membrana-propria of the testicular cavity. These 
germs are situated in a common mass of protoplasm, which may become 
the caducous protoplasm. The germ nuclei acquire a proper protoplasm, 
and so become proto-spermatoblasts. A head is formed for the sper- 
matozoon at the expense of a portion of the nuclein of the cell, while 
the rest forms a cephalic hood. Mitotic division is twice repeated for 
these cellular elements, and in this way we arrive at the trito- spermato- 
blasts. Radiated or caudal filaments are formed at the expense of the 
cytoplasm, and there is some resemblance to the spermatozoa of Locus- 
tidse, on which the author remarks. 
Cephalic Neural Crest of Selachii.§ — Sig. A. Coggi describes in 
Torpedo and Pristiurus, in the region of the fore-brain, a portion of the 
neural crest, which he calls the anterior ganglionic ridge ; its elements 
arise from the cerebral wall and from the ectoderm, as in the other parts 
of the ganglionic ridge ; but its role appears to be that of passive mesen- 
chyme, for it is not associated with the origin of nerves. The character 
of passive adaptability is elsewhere illustrated in other parts of the 
ganglionic ridge. The first division ot the neural crest is due to hyper- 
trophy of epidermic cells in the auditory region ; thus a pre-auditory 
and a post-auditory region are distinguished. A further division is 
associated with the appearance of the trigeminal and facial in the pre- 
auditory region. Thereafter the trigeminal group is divided in its 
ventral portion, “ the ganglionic lamina,” into two parts, belonging 
anteriorly to the ciliary, posteriorly to the trigeminal proper, and so on. 
In these partitions the ganglionic lamina is passive, and subject to the 
influences exerted on it by epidermis, cerebral wall, somites, and gut. 
Of importance also are its relations with a transitory superficial sense- 
organ, one of Kupffer’s “ placodes,” which is divided into an anterior 
' portion in relation with the ciliary and a posterior portion in relation 
with the trigeminal proper. 
Development of Egg in Flat-fishes and Pipe-fishes. |j — Mr. J. T. 
)i Cunningham has been directing his attention to a history of a definite 
* Anat. Anzeig., x. (1894) pp. 332-3. 
f Comptes Rendus, cxx. (1895) pp. 205-8. t See ante, p. 156. 
§ Atti R. Accad. Lincei (Rend.), iv. (1895) pp. 265-9. 
\\ Journ. Mar. Biol. Assoc., iii. (1895) pp. 258-70 (3 figs.). 
u 2 
