718 JOHN BEARD, 



From the start there was a natural suspicion, that the larger 

 number of primary germ-cells related to the female embryos. I had 

 no certain knowledge of the relative numbers of the two sexes in 

 Baja hatis\ and, moreover, the number of such germinal areas in my 

 possession was not great enough for statistical purposes^). I was 

 thus obliged to determine the relative numbers of the primary germ- 

 cells in embryos, in which the sex, though not yet announced, was 

 betrayed by one or other of the well-known characters, a knowledge 

 of which we owe to Semper. The result of this further census demon- 

 strates, that in embryos potentially female the number of primary 

 germ-cells is double that in embryos potentially male. 



As such embryos are relatively in embryological sense "late or 

 older embryos", it cannot be expected, that the total number of pri- 

 mary germ-cells will always be found to be 255 or 511 — the de- 

 generation of some or many of them may already have taken place. 

 In potentially male embryos the number of primary germ-cells is, 

 however, always such as to be derivable from 256, in potential females 

 from 512, and from these two numbers respectively and 

 only ^). 



Lest too much stress should be laid upon this fact, let another 

 one be added to it. I had, perhaps not unnaturally, expected to find 

 a similar sexual difference in other Elasmobranchs, thus in Scyllium 

 canicula; and to this end the primary germ-cells of 7 embryos 

 of this fish were counted. The variety of this species at my disposal 

 was obtained in Wales. I believe it to be in some respects distinct 

 from, for instance, the Neapolitan form. Therefore, it by no means 

 follows, that the like conditions will be found in the latter variety. 

 In 4 potentially female embryos and in 3 potentially male ones of 

 S. canicula the number of primary germ-cells was found to approxi- 

 mate to 128. From this it may be concluded, that here the number 

 is alike in both sexes. 



female skate was verified. As was anticipated, the males are smaller 

 from end to end, and also across the broadest part of the pectoral fins. 



1) So far as they went, the study of germinal areas of the smooth 

 skate seemed to point to an equality in numbers of the two sexes. 

 From statistics, kindly furnished by Mr. P. Jamieson, of the staff of the 

 Scottish Fishery Board , this conclusion finds its warrant in fact. 

 Among 1486 smooth skate he found 735 females and 751 males. 



2j The actual figures and tables will be published in Pt. 3 of the 

 memoir on the germ-cells. 



