4 
1891.] ` Zoology. 491 
little seems to be known of their development. Rathke is, so far as 
I know, the only one who has studied it; his account deals merely 
with superficial appearances, and is therefore very incomplete. 
I have been able to make out a few points in the early history of 
these organs from specimens collected in July, 1890, at the Marine 
Biological Laboratory, at Cold Spring Harbor, Long Island. My 
specimens were mostly embryos of the black snake (Bascanium con- 
strictor), of from the second to the ninth week of embryonic life, 
together with a few garter snake (Zuéenia sirtalis) embryos, taken 
at a considerably later stage in their development. 
First, a word on the general anatomy of these organs. The male 
copulatory organ in snakes, as in lizards, is made up of two distinct 
parts, Each part is in the form of a long, hollow sack, more or less 
irregular in outline, and in some species bifurcated at the end. A 
thick layer of connective tissue, containing numerous cavities in its 
outer portion, forms the greater part of the walls of this sack. These 
cavities are connected by a branch with the dorsal artery, and it is by 
a flow of blood into them that erection of the penis is accomplished. 
Outside of this connective tissue is the epithelium, a continuation 
of that covering the rest of the body. This epithelium consists of two 
layers. The inner, called by Neumann the “stratum mucosum,”’ is 
made up of large, columnar cells arranged side by side, and containing 
prominent nuclei; the outer is a layer of very much flattened cells 
with deeply staining nuclei, joined by their edges to form a thin cov- 
ering to the whole. 
On the inner side of each penis, running obliquely from base to 
tip, is the semen canal. This is a deep depression, approximately 
anchor-shaped in cross section. During copulation the two parts o 
the penis are brought together in such a way as to make of these two 
canals one long tube, which then serves to conduct the semen into the 
oviduct of the female. 
Closely set all over the surface of the penis are numerous cartilagi- 
nous teeth-like bodies, which arise in the connective tissue, and pro- 
ject out through the epithelium. Their exact function is not known, 
though they have been regarded as “‘ wollustorgane,’’ or contrivances 
for stimulating the sexual organs. It is possible that they may serve 
to hold the sexes more firmly together during the act of copulation. 
These penes arise as external appendages. At the close of embry- 
onic life, how however, they are drawn back into two pouches, one on 
either side of the body just behind. the cloaca, This action is effected 
Š Entwicklung. der Natter. Königsberg, 1839. 
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