SCIENTIFIC SUMMARY. 
329 
of the superincumbent water (teeth of fishes and shells of Pteropods), and 
others are brought by currents from littoral regions (bones of the Manatee, 
and fragments of littoral plants). All the branches of the animal kingdom, 
so far as their marine carnivorous orders are concerned, are abundantly 
represented in this region, but it is destitute of plants. The third region is 
sparsely inhabited by a few Mollusks, Kadiates, and Crustaceans, but the 
peculiar animals are the microscopical Globigerinje whose siliceous shells 
have covered the bottom of the channel with a thick deposit. The deep-sea 
animals of the second and third regions are of smaller size than allied forms 
of the littoral zone. The only exception is an Echinus, which is nearly of 
the average size, and an Actinia. 
The American Lepidoptera. — The American Entomological Society is now 
issuing in parts a list of Butterflies and Moths. The editors are Messrs. 
Grote and Robinson. 
American Grasshoppers have been equally well dealt with in a catalogue 
prepared by Mr. Samuel Scudder. 
The Vascular parts of the Retina of the Hedgehog. — The Proceedings of the 
Royal Society, May, contains a communication by Mr. J. W. Hulke, in con- 
tinuation of his former papers on the structure of the retina. The chief 
peculiarity, he says, is that only capillaries enter the retina. The vasa centralia 
pierce the optic nerve in the sclerotic canal, and, passing forwards through 
the lamina cribrosa, divide at the bottom of a relatively large and deep pit 
in the centre of the intraocular disc of the nerve, into a variable number of 
primary branches, from three to six. These primary divisions quickly sub- 
divide, furnishing many large arteries and veins, which, radiating on all sides 
from the nerve- entrance towards the ora retinae, appear to the observer’s 
unaided eye as strongly projecting ridges upon the inner surface of the retina. 
When vertical sections parallel to and across the direction of these ridges are 
examined with a quarter-inch objective, it is immediately perceived that the 
arteries and veins lie, throughout their entire course, upon the inner surface 
of the membrana limitans interna retinae, between this and the membrana 
hyaloidea of the vitreous humour, and that only capillaries penetrate the 
retina itself. 
The development of the Zoosperms of Fishes forms the subject of a paper 
published in the Bulletin of the Academy of Sciences of St. Petersburg, 
by M. OwsiannikofF, whose researches on the zoosperms of the salmon and 
other fishes lead him to conclusions quite opposed to those of Kolliker. The 
cells which develop the zoosperms may, he says, sometimes be seen to con- 
tain from ten to fifteen secondary cells within them, and these are the young 
spermatozoa. The nucleus of the cell becomes the head, and the protoplasm 
which surrounds it forms the tail. The adult spermatozoon has a head like 
an ace of hearts,” pointed in front and broad behind. It consists of two 
lateral parts, which are separated by a superficial groove. Immediately 
behind the head there is a thickening of the tail, which however has no 
special feature. The zoosperm does not move along by jerks, but by a dis- 
tinct undulating motion. When water is added to the seminal fluid the 
zoosperms move about briskly, but when much is added the tails disappear. 
This, the author says, is due to a retraction of the tail towards the head, and 
a coiling of the former round the latter. 
