25 ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 



the latter being of special interest with regard to a comparison with the Plagiostomes; it is much 

 thicker than the M. dilatator, and covers the lateral surface of the stem-piece b^, and of the piece b 

 to the terminal part. Into this muscle sinks through the dorsal appendix-.slit a continuation of the 

 outer skin as a «glandular-bag , which on account of its simplicity might be called ■rudimentary*, 

 when compared to that of the Plagiostomes, as it has e\-idently remained in a similar stage of 

 development as that, with which it begins in those; by a further development forward and \-en- 

 trally a quite similar glandular bag would arise as the one described as characteristic in the Pla- 

 o-iostomes. The direction of the fibres of the M. compressor is rather peculiar in the Holocephales 

 (see the special part); here I shall onh' mention that part of the fibres seen dorsally (fig. 70I, runs along 

 the lateral edge of the appendix-slit rather straight from the piece /5 backward in quite the same 

 manner as in the corresponding part, the outer lip-muscle:», of the M. compressor in the Plagiostomes. 

 The whole structure of this muscle forms, as it seems to me, an incontestable proof as to the correct- 

 ness of m\- interpreting the muscular coat of the glandular bag of the Plagiostomes as part of the 

 skeletal muscles proper. 



In the female the whole muscular system of the appendix is wanting; according to v. Da- 

 vidoff the little terminal joint has an attachment for part of the dorsal muscles arising from the 

 wall of the bodv (i. c p. 477, pi. XXIX, fig. 18, ps\ corresponding to the attachment of the same muscle 

 on the piece b^ in the male; just on account of this v. Davidoff explains the terminal joint to be 

 homologous with this piece. 



The fin-muscles of the male have been rather slighth' treated in the earlier literature; a com- 

 parison between several forms has been almost quite out of the question, onh' a few forms having been 

 described. Thus among the Sharks AcaiitJiias has already been mentioned by Bloch, among the 

 Rays some /liT/'c? - species by several authors [Raja radiata very briefly and incompletely by Bloch, 

 Raja circular is |or clavata] by Duvernoy, R. clavata by Vogt &. Pappenheim and later by 

 Moreau), Cliimccra moitstrosa by v. Davidoff. Petri alone has examined several different forms 

 and tried to make a comparison, but he cannot be said alwa>s to have been successful or to have 

 found the correct interpretation. While he upon the whole pretty correctly has interpreted the muscle 

 I have called M. adducfor, — his AI. flexor pinner^ or pferygopodii\ a name rejected by me as presum- 

 ably not suitable, — and AI. dilatator, a name introduced by him (at all events in Scyllium, Acantliias 

 and Torpedo), the other muscles have either been misapprehended or not at all mentioned. The M. extensor 

 he has only seen in Scy Ilium and Raja, where he calls it M. flexor pterygopodii interior, and of my 

 M. compressor he has only mentioned the part, which I have called the outer lip-muscle (of the 

 appendix-slit), in xlcanthias and Raja, and with different appellations, respectiveh" as M. levator (of the 

 spur) and as AI. flexor biceps (which latter name is also given to a quite different muscle in Scyllium), 

 and he has assigned to it different, partly misapprehended, functions. It has already been observed 

 that both Petri and all other authors, who have mentioned the glandular bag, have understood the 

 muscular wall to be a separately developed dermal muscular system, and consequently omit it by the 

 mentioning of the fin-muscles proper. In the special part account will be rendered of the earlier 

 literature, and the particular works will be referred to. 



