473 



existence, either in size, characters of the two sets of cells, or their 

 positions in the embryo. It is imperative, because without the "mega- 

 spheres" the missing germ-colls of earlier embryos cannot be accounted 

 for, in default of mitoses among the few normal and ordinary germ- 

 cells in any embryo of 6 mm. The degenerative phenomena in both, 

 and the peculiarities of their nuclei point in the same direction. 



Lastly, in the later embryos of upwards of 20 mm the practical 

 replacement of the "megaspheres" by undoubted germ-cells in abnormal 

 situations is a fact of like significance. 



The writer quite anticipates his interpretations being deemed by 

 some to be absurd: but he is equally prepared to witness the complete 

 failure of any attempt — based on actual work! — to prove the 

 "megaspheres" to be anything other than germ-cells. 



The present work was undertaken and carried out without bias. 

 And, having no theoretical ends to serve, no phylogenetic hypothessi 

 to set up, the writer can conscientiously claim to be free from any 

 bias, except in favour of the truth. The interpretation has been tested 

 in every way ; and, finally, adopted as completely explaining the facts. 

 No other interpretation does this. In fact, there is no other con- 

 struction in existence. 



If the "megaspheres" always occurred in like numbers, sizes, and 

 places in every embryo, they might represent, as Hoffmann thought, 

 stones of the embryonic edifice. They are never alike either in position, 

 size, or number in any two embryos. The writer has seen them again 

 and again in the past twelve years; more recently he has studied them 

 to and beyond the period, when as "megaspheres" they cease to exist. 

 Never once has the slightest indication been remarked 

 of any attempt on the part of one of them to form any 

 portion of an embryonic organ. On the other hand, the figures 

 drawn and the many instances studied all go to show the above inter- 

 pretation to be correct, as it also is the only possible one. 



If "megaspheres" be not germ-cells, then many apparent gerra- 

 ceUs are not such ; as examples : those of figs. 8, 9, 16, 24, 25, 28, 

 and 34 to 36. And, indeed, it is to be feared, that we shall never 

 be in a position to determine with any degree of certainty at all, what 

 is a germ-cell in a skate-embryo ! 



The final possibility of a genetic connection of "megaspheres" and 

 "merocytes" is disposed of by the twin-nuclear condition of the former, 

 especially as revealed in those which degenerate, thus in figs. 46 and 47. 



The "megaspheres" within the embryonic area being now identified 



