198 



bryos, some of the germ - cells may, and probably have, degenerated. 

 In no. 182 some sections were missing. The average found is 114.75 1). 



For Pristiurus the results have already been given : here the aver- 

 age number is about 127 (Anat. Anz., Bd. 21, p. 53). 



Acanthias vulgaris — early embryos only — is a very favourable 

 object for the study of the germ-cells, when one can obtain the em- 

 bryos in a well-preserved condition. Although many series of such 

 embryos have been prepared, so far only in two of those examined 

 was the preservation perfect. In my notes it is stated, that the count 

 was an easy and accurate one, for the germ-cells were far apart. The 

 embryos are, also, relatively much larger than those of Scyllium and 

 Pristiurus. The total is apparently smaller than in the latter two 

 forms. 



In both embryos numerous vagrant germ-cells were noted. Leav- 

 ing out of account those on or within the splanchnopleure, in the one 

 instance there are 17, in the other 21 "elsewhere". The places in- 

 cluded embrace somatopleure, body -cavity, epiblast, gut -epithelium, 

 beneath epiblast, and nephridial tubules, in all of which germ -cells 

 were found. 



The total 2) in each case is the like one, 51. Owing to the small- 

 ness of the embryos — about 6 mm — some of the germ-cells may 



there are more rudimentär}^ tubules in potential females of Scyllium and 

 Pristiurus. In Scyllium I have found the number to vary from 6 — 8. 

 And with but two such rudimentary tubules Raja is supposed to be 

 — by some only — a "highly specialised Elasmobranch!" 



1) In Scyllium canicula embrj^os thero are always a few more germ- 

 cells on the actual left side of the middle line than on the right. 



2) What 2n really is in Acanthias cannot at present be stated 

 with certainty. Some thirty or more of its embryos have been cut, of 

 these but two were preserved by the writer. These two , obtained in 

 the fish-market at Triest, were about the worst of the whole lot! In 

 two others, whose germ-cells were tabulated since writing the above, 

 the following finds were made. Acanthias no. 11 (5 — 6 mm), total germ- 

 cells 34, of these 8 were vagrant, three of them being upon the somato- 

 pleure, one in the body-cavity. The embryo was probably somewhat 

 abnormal, i. e., one doomed to degeneration. Acanthias no. 36 (circa 

 12 mm) total germ-cells 116, of these 19 were "elsewhere". Several 

 were upon the somatopleure, 3 on the subintestinal vein, 2 in nephridial 

 tubules, and 1 in the body-cavity. Many were in degeneration, forming 

 concentric capsules. 



2n in Acanthias may turn out to be 128, or 128 and 64. 



The writer would be grateful to any embryologist , who would 

 place a set of well-preserved early embryos of Acanthias at his dis- 

 posal, or who could inform him where such might be easily obtained 



