The germ-cells. 623 



of which even those current in book-forna are devoid of any real 

 groundwork of original observation. 



After all, then, the result of the work of thirty years past has 

 given us two sharply defined theories of the origin of Vertebrate 

 germ-cells, with a possible couple more, not at all well worked out. 



Of these one has held the field — it is difficult to say why. The 

 other is nearly as old, but it has never succeeded in making much 

 headway against its more fortunate opponent. The latter, indeed, 

 remains in the position it occupied in 1871, so far as the support of 

 facts is concerned. And, it must be admitted, the former has only 

 obtained substantial support in recent years from the researches of 

 Eigenmann. These are little known, and, perhaps because standing 

 almost alone, they have been completely ignored. 



Surveying broadly our supposed knowledge of the germ-cells in 

 the Vertebrata — even if all the statements of standard books were 

 fact — one must be struck with the slight amount we really possess. 

 The researches of recent years are not numerous. Born only records 

 15 memoirs in his review. Since 1894 very few papers have appeared. 

 Indeed, the total of the thirty years does not nearly approach the 

 list of papers on the peripheral nervous system, the nephridia, or, to 

 name a classic object, the history of the blastopore. 



And these are the years, which have witnessed Weismann's work 

 on the Hydrozoa, his series of classic papers on the continuity of 

 the germ-plasm, and a legion of memoirs on the germ-cells of all 

 sorts of animals ! 



Continuity of the germ-plasm! Continuity of germ-cells! These 

 are taught in our universities, but our embryological text-books fail 

 to tell us anything about them in the important sub-kingdom, Verte- 

 brata. The information they do furnish regarding the early history 

 of the germ-cells is not in accordance with the facts! 



Why is it? Possibly, as Born suggests, our methods are at fault. 

 In the ways we usually prepare and treat an embryo for instruction 

 or research it is little enough we see of the germ-cells. In my im- 

 mense collection of Elasmobranch embryos, more especially of the 

 skate, there are many series of preparations, which even a professional 

 embryologist, who had not specially worked at the germ-cells, might 

 examine without seeing a single germ-cell. And yet the preparations 

 are perfect and for many purposes exquisite. There are thousands 

 of preparations in my possession, and, possibly, thousands upon 

 thousands in the collections of other embryologists, in which it would 



