Miscellaneous. io 
outer capsule of the eye, and bears the cornea: another more closely 
envelopes the retina; it is cartilaginous, serves for the attachment of 
the muscles of the eye, and reminds us of the sclerotic ring of birds 
and reptiles. Even in the Nautili, however, there no longer remain 
any of these homologous parts of the sclerotic. In the other Mol- 
lusea it would be very difficult to say what we are to regard as the 
sclerotic. It is equally impossible to distinguish a cornea in them. 
We cannot say, indeed, that the essential character of the cornea is 
its being the first refractive medium in the eye. The serpents teach 
us the opposite of this, since in them the first refractive medium is 
formed by the eyelids. Moreover, in a great number of Mollusca, 
the region which is usually designated by the name of the cornea 
does not present any greater transparency than the rest of the en- 
velopes of the eye. 
In the Vertebrata, on the contrary, the cornea has a very definite 
meaning, especially as, from the observations of M. Hensen, it pre- 
sents a development sui generis. In the embryo, immediately after 
the invagination of the crystalline, this anatomist has seen the 
cornea appear as a very delicate basilar membrane of the epithelium. 
As long as the crystalline still contains a cavity there exists between 
it and the cornea, in front of the pupillar membrane, a sort of gela- 
tinous tissue, exactly similar to that of the vitreous body at the 
same embryonic period. Neither the sclerotic nor the choroid has 
any connexion with a similar tissue. 
It is equally difficult to determine the homologue of the choroid 
in the Mollusca. In the Vertebrata this membrane is at once vas- 
eular and pigmentary. The concordant investigations of MM. Kol- 
liker, Hensen, Schultze, and Steinlin show clearly that the black 
epithelium of the choroid is in reality a dependency of the retina; 
it is formed, in fact, by the outer lamella of the primitive ophthalmic 
vesicle. M. Hensen asserts that he has ascertained that the cones 
and bacilli are produced by this epithelium and not by the rest of 
the retina. Hence the principal character of the choroid is vas- 
cularity, and the name of vasculosa has frequently been given to it 
in human anatomy. From this point of view it would be impossible 
to find the least trace of a choroid in the Invertebrata. The intra- 
retinic pigment layer of the Mollusca in particular by no means 
merits the name of choroid. 
It is generally supposed that the ophthalmic vesicle which sub- 
sequently forms the retina is nothing but an extravagination of 
the central nervous system. The embryological researches of M. 
Hensen tend not only to confirm this view, but also to establish a 
complete parallel between the different layers of the retina and those 
which primitively form the central nervous tube.—Archiv fir 
mikr. Anat. Bd. ii. 1866, p. 399; Abstract by E. Claparéde in Bidl. 
_ Unw. November 25, 1867, Bull. Sci. pp. 268-271. 
Adanson’s Black Crocodile. By Dr. J. E. Gray. 
_ Dr. Alexander Strauch asserts that Adanson’s “Crocodile noire” 
is not Crocodilus frontatus, but C. cataphractus. Adanson mentions 
