r 6 ON THE APPENDICES GEXITALI-S (CLASPERS) IN THE GREENLAND SHARK. 



the bag has already been pressed towards the ventral side as well as the other surrounding layers 

 of tissue. 



b. Intimately connected with the other muscles of the glandular bag is found a powerful 

 muscle (pi. V, fig. 59, 61 and 62, S), seen on the dorsal side, where it forms the lateral lip of the long 

 slit (of), \\ hich is the entrance to the bag. It takes its origin from the two hindmost rays (sometimes 

 also having bundles from the last but two) as also from the lateral surface of the piece /?, covered 

 by the superficial layer (O) coming from the muscles of the body; it is inserted in the tendinous 

 tissue passing over the head of the thorn ( 7V), and firmly connected with the proximal end of the 

 terminal piece TV, especially with its edge; in this tissue is found imbedded several firm, fibrous 

 portions, which partly calcify, and probably - - in more developed stages — form a separate piece 

 ( /: : .). In the hindmost part this muscle is completely fused with the distal part of the muscles 

 of the glandular bag, and anteriorly it forms a whole with the above mentioned bundles of the dorsal 

 wall of the bag, which arise from the ventral side of the two hindmost rays; in the interspace a 

 kind of separation is effected by the attaching of the fin-membrane, the connective tissue of which 

 wedges in between the lip muscle and the wall of the bag itself. This muscle acts antagonistically 

 to M. dilatator, which in a preparation is easily seen by pulling it: thus when M. dilatator by contracting 

 has dilated the groove between the terminal pieces, as described above, and the thorn stands out, the 

 contraction of this outer lip-muscle of the appendix-slit will again straighten the groove by especially 

 acting on the piece Tv, and at the same time carry back the thorn , so that it will lie against the 

 piece Tv. 



I find the same muscle in all other Plagiostomes, but in very different stages of development 

 (cp. the following). Petri has mentioned it in Acauthias, but as J/, levator of the thorn (I.e. fig. 5, 

 B, C, F, ml); he says: Er inserirt sich hinten vermittels eines starken, sehnigen Bandes am vorderen 

 Theil des Spornes («the thorn ) und hat allein die Aufgabe diesen zu heben. This, however, is quite 

 incorrect: it is not inserted on the thorn, even if its tendon of course by looser tissue is connected 

 with the proximal part of the latter, but on the piece Tv (l>'" in the figures of Petri), of which piece 

 Petri's interpretation is quite wrong (cp. the following); and it does not assist the M. dilatator, nor 

 raises the thorn, but it counteracts the M. dilatator, and thereby becomes a J/, depressor of the thorn! 

 The carrying back to the position of rest of the terminal pieces is in the Greenland Shark and 

 Acanthias not exclusively brought about by an elastic reaction of the tissues between the firm parts 

 of the skeleton, as asserted by Petri (I.e. p. 303), but this reaction, which certainly exists, is also 

 supported by the action of muscles belonging to the glandular bag, or, at all events, forming part of 

 its muscular system. Taking it for granted that the appendix genitalis by the copidation is really 

 introduced into the cloaca of the female, I imagine the following act to take place: the appendix is 

 guided "and brought into the cloaca by means of the muscles belonging to and arising from the fin- 

 muscles proper; next the M. dilatator will come into function, and, by its dilating the terminal parts, 

 fix the appendix in the cloaca, and then the muscles of the glandular bag will evacuate its contents 

 into the furrowshaped, in the appendix itself situated part, the walls of which at the same moment 

 will contract, at the same time ejecting the secretion and letting go the firm hold of the apppendix. 

 As I think the chief action of the muscular wall of the glandular bag to be the ejection of the 



