630 JOHN BEARD, 



No. 454, but in dozens of other embryos also, it appears probable, 

 that in their early history, a period lasting until all their yolk is used 

 up, the germ-cells are cells of practically the same cell-generation. 

 The word "practically" has been used, because, as will appear anon, 

 ia earlier embryos some of the germ- cells — a varying number — 

 may be much bigger; and from this it may be concluded, that they have 

 not completed the number of divisions, one, two, three, or at most 

 four lacking, to bring them to the "resting phase". This phase is a 

 very real thing in my embryos: indeed, it was noted long ago by 

 Balfour (78). 



Mitoses of germ- cells have been diligently sought for in many 

 embryos of sizes 8 mm to 42 mm, and the result has been the soli- 

 tary mitosis figured in fig. 32. The result of this quest may seem to 

 have been in inverse proportion to the time and labour expended; but 

 in research it is unfortunately often the little facts, which give most 

 trouble. 



And it has been deemed desirable to carry it out for another 

 reason. Minot ('94), possibly on the ground of researches (?), 

 which he has never yet (1901) published, has strongly dissented from 

 Balfour's, Semper's, Rückert's and Rabl's conception of the germ- 

 nature of the cells called by them "primitive ova". He is of opinion, 

 that the "theoretische Erklärung dieser Zellformen wahrscheinlich durch 

 Betheiligung zur Zelltheilung zu suchen sei". Leaving Rabl's work^) 

 out of question, for it was overlooked by Minot, it certainly does 

 seem a strong and unusual course, impossible of justification, to sug- 

 gest that an investigator like Rückbrt, who has won laurels in this 

 very field of cytology, could mistake a cell in any phase of mitosis 

 for anything else. It would be a much worse blunder than the as- 

 serted taking of mesodermal cells for ganglion-cells! 



In all my preparations of Raja hatis, while mitoses are as com- 

 mon as blackberries in autumn in other parts of the embryo, the 

 germ-cells for a prolonged period, i. e., after they enter into the 

 resting phase, are sharply marked off from cells of the 

 embryo by entire absence of mitoses among them. Every- 

 where else one easily finds mitotic figures, in the germ-cells practi- 

 cally never. 



Returning to the table, the number of germ-cells counted tells 

 its own tale, but that number is not complete. 



1) Rabl's rejoinder will be found in : .Morph. Jahrb., V. 24, p. 755. 



