246 W. HAROLD LEIGH-SHARPE 
the cloacal aperture, while in the skates it is some considerable 
distance posterior to it, an inch or more in a moderately sized 
adult. 
Leading into the apopyle by a narrow aperture, so as to com- 
municate with the clasper tube, on either side, is a large cavity, 
the siphon, a sac with extremely muscular walls, situated imme- 
diately below the corium of the ventral surface of the abdomen, 
frequently several inches in length, close to the median line, 
and ending blindly, having no communication with the coelom, 
and whose function and significance it will be my endeavor to 
elucidate. 
In the skates, on the other hand, no such hollow sac is found, 
but its place is taken by the clasper gland, contained in a sac 
which it completely fills. This gland has long been recognized, 
but its containing sac does not appear up to the present to have 
been demonstrated to be homologous with the clasper siphon of 
the sharks and dogfish, which is but little known. 
Other accessory structures may be present on the claspers, 
such as the spurs and the like in Acanthias, but of these none 
attains such importance and is more frequently present than a 
fan-like expansion at the distal end of the clasper, the rhipidion, 
whose function is to spray the spermatozoa in all directions in a 
radiating manner. If a jet of water, as from a garden hose, be 
directed against a flat surface, e.g., a piece of board, at such an 
acute angle as to be almost parallel with it, the water will fly 
off from the edges in directions corresponding to the shape of 
the margin of the board. If the board be fan-like at the edge, 
the water will radiate equally all round the quadrant. The 
rhipidion attains a greater development in the skates than in 
the sharks. 
After this brief introduction, an insight into the topography 
and actual function of the siphons can best be gained by con- 
sideration of the first example under survey, Scyllium catulus, 
which will be treated more fully than the rest as a typical example. 
It must be borne in mind, however, that the figures are not 
drawn so as to show the claspers in their natural position, but 
deflected in such a way (usually inward, though occasionally 
