96 Miscellaneous. 
specimens. The Selachian genera in which I have regularly found 
them in sexually mature adult individuals are as follows :—Squatina, 
Scymnus, Centrophorus, Spinax, Acanthias, Hexanchus (in a speci- 
men 10 feet long), Pristiurus, and Scyllium. In the last genera - 
they are very small, and for the most part also altered; on the 
other hand, in Scymnus and Squatina they are exceedingly large, 
furnished with distinct funnel-shaped apertures, into which fine 
forceps may be conveniently introduced, and are present high up on 
the sexual fold. In Squatina especially these organs are so numerous, 
regularly developed, and striking even in the living animal, that it 
is quite incomprehensible to me how they can. have been hitherto 
overlooked. he following genera are destitute of them when 
adult—Lamna, Mustelus, Galeus, Carcharias, and probably Sphyrna ; 
when they disappear, or whether they occur at all in the embryo, 
still remains to be ascertained. 
In my first communication I indicated that perhaps the seminal 
ducts originated from the segmental funnels. This is decidedly not 
the case; but, on the contrary, it seems probable, especially from 
their behaviour in Squatina, that the segmental ducts may become 
the vasa efferentia testis; and by a growth of the epithelium of the 
segmental funnels the epigonal organ may perhaps be produced. 
In favour of the supposition that the primitive renal duct becomes 
the seminal duct we seem to have the two facts :—that in large male 
embryos only a single canal is to be found, which subsequently 
becomes the urino-seminal duct; and, secondly, that a tuba occurs 
in the males of all genera of Rays and Selachia, and passes on each 
side into a canal exactly as in the females, and this evidently can 
be nothing but the anterior end of the primitive renal duct. The 
middle tubal orifice of the males is very large in many genera 
(Seymnus, Centrophorus, Squatina); the canals running backwards 
from it (representing the oviducts of the female) are very soon 
obliterated, and cannot be traced as such to the kidneys in the 
genera which have hitherto been investigated. In a few species, 
only a fine cord, but without a cavity, was recognized between the 
kidney and the hinder extremity of the male tubal canal. Careful 
investigations of the embryos have proved, however, that the per- 
manent urino-seminal duct of the male is not the primary primitive 
renal duct, and that the latter disappears almost entirely in the 
region of the kidneys, whilst, as in the females, a secondary primi- 
tive renal duct has been developed as a urino-seminal duct. This is 
the case also in Chimera. In the males of this species there are 
two isolated tubal openings which lead into a fine canal lying upon 
the urino-seminal duct; this corresponds in position to the oviduct 
of the female, and can be nothing but the primary primitive renal 
duct. By this Chimera approaches much more closely to the 
Ganoids than to the Plagiostomi. 
I hope soon to be in a position to follow up my first memoir, 
which has already been referred to and will shortly appear, on the seg- 
mental organs of the Selachia and the relationship of the vertebrate 
and invertebrate animals, with another on the urogenital system 
of the Plagiostomi.—Centrclbl. fiir die med. Wiss-nsch. 1874, no. 52. 
Wurzburg, Oct. 1, 1874. 
