SEXUAL CHARACTERS—ELASMOBRANCH FISHES 251 
Though the correlation of the previously mentioned structures 
is sufficiently remarkable, matters are rendered still more com- 
plicated by the presence, at least in Scyllium catulus, of another 
pair of blind saes, smaller in size, but of a similar nature to the 
siphons; situated in a like position, but nearer to the median 
line than the siphons proper, which, as far as I can discover, have 
never previously been described. They are vestigial in S. 
canicula, and only occasionally found in that animal. In order 
to distinguish them from the larger siphons, they will be referred 
to as the parasiphons (fig. 1, P). 
While the sinhonal tube is set at an angle to the apopyle, the 
parasiphonal tube is in the same straight line with that orifice. 
The apertures of the siphon tube and the parasiphon tube are 
situated in a common exedra. 
I can but regard the parasiphons as accessory to the siphons. 
In the present case they are 0.9 inch in length, have similar 
muscular walls, and are capable of inflation and distention by a 
ball pipette, proving that they have no internal opening into the 
coelom. They are located dorsal to the skeletal rod of the 
clasper, and therefore in figure 1 their indicated inflation is 
purely diagrammatic. 
Situated within the extracloacal aperture, on either side of 
the urogenital papilla are a pair of pocket-like depressions, the 
cloacal pouches, attached in front of which are the cloacal 
papillae with their apices directed backward. ‘These structures 
are so well known to everybody as to need but passing mention. 
They are not present in all elasmobranchs. 
Each papilla is perforated by a peritoneal canal, which leads 
anteriorly from the coelom, and opens posteriorly by the abdom- 
inal pores into the cloacal pouches. ‘The pores are wide in this 
species, but are open only in mature dogfish. 
The histological details of the structures under consideration 
are dealt with under 8S. canicula, material of that species being 
more available, while, in order to enable investigators to deter- 
mine the presence or absence of spermatozoa in the siphons in 
reenacting the foregoing experiments, a figure of a spermatozoon 
is introduced (fig. 4). 
