8o ON THE APPENDICES GENITALES 1CLASPERS1 IN THE SELACHIANS. 



of the slit approach the cloaca of the animal itself (as supposed by Agassiz [and Garman]); neither 

 can a turning round the longitudinal axis be effected (least of all a turning of i8o : ' , as would be re- 

 quired in the Skate), and thus any thought of a putting together of the slits of the two sides to form 

 a tube (Agassiz, Giinther) has to be dismissed (quite apart from the fact that in some forms - 

 Scyllium, Pristiurus - the appendix-slit is closed for a long way by coalescing). A putting together 

 of the medial sides of the two appendages may however easily be effected by the Muse, adductores, 

 but by this no convenient wav for the sperm would be formed; and the observation of Bolau 

 shows moreover that in Scyllium only one appendix is used at a time; for the present it may, how- 

 ever, be disputed, whether this is a universal law in all cases and in all other Selachians. Thus it 

 seems that the tubular, or rather semi-tubular form of the appendix cannot directly have anything to 

 do with the transferring of the semen; the most immediate purpose of this form evidently is the 

 transportation of the gland-secretion. 



On the other hand the structure of the appendix shows with still greater certainty — quite apart 

 from the observation by Bolau -- that the appendix cannot be used for externally clasping the 

 female. For a great part, I think, it is the hooks, claws, or thorns, so often projecting through the skin 

 of the terminal part that have caused or supported this supposition. But an attentive observation of the 

 position and way of moving of these firm parts, as also of the whole constitution of the terminal part, 

 might, as it seems to me, rather easily have persuaded the many adherents of the theory of these organs 

 as claspers , or Klammerorgane , that thev are only ill adapted for such a purpose. The skin of the 

 whole terminal part is, as we have seen, often quite naked and soft (the point itself is always so), and 

 the appendix would therefore -- as has been correctly pointed out by Agassiz — be badly off with 

 regard to the rough surfaces, with which in most cases it would have to do, and against which it 

 would only be slightly protected by the secretion (Bloch; this secretion would rather be a hindrance 

 for the clasping, as is also remarked by Davy). In the i&a^Iz-species the hard skeletal parts whose 

 business would be to hold fast the female, only appear within the dilated terminal part, and are 

 wrapped by a specially vulnerable skin, very much like a mucous membrane; consequently, if these 

 parts were to hook on — for which their special shape is in no way adapted — for inst. to the thorny 

 tail of the female Ray (Cuvier & Valenciennes, Dumeril), their most immediate surroundings 

 would he much exposed to injury; and if we choose to regard such appendages as those in Acanthias, 

 Somniosus, or above all Spinax, which, by the hooks, thorns, or claws projecting freely through the 

 outer skin, may for a superficial examination convey the impression of being plain prehensile 

 organs (the dilated terminal part of Spinax reminds not a little of a bird's foot!), then any closer 

 examining will show that they cannot be such: the position of these claws is always so, that they 

 cannot catch an object, or clutch it. Besides their movement inward, against each other, when the 

 terminal part is closed, always takes place with small force, by elastic reaction of the connecting soft 

 parts, only to a small degree (and not in all cases) somewhat assisted by muscular action. The erec- 

 tion of these parts on the contrary, when the terminal part is opened bv means of the always power- 

 ful M. dilatator, can take place with great force, and they may with force be kept spread out. I 

 think therefore that there can be no doubt, but that Davy has had an eye for the correct fact (al- 

 though the Rays especially examined by him, do not present the fact so clearly by far, as do Acanthias 



