The Germ-cells of Lophius. 567 



Cyclostomata: Amphibia: 



Wheeler, 1900, lamprey Nussbaum, 18S0, Ranafusca 



^ Alien, 1907a, Rana pipie7is 

 Elasmobranchia: King, 190S, Bufo lentiginosus 



Balfour, 1876, Scyllium "Kuschakewitsch, 1908, Rana esculenta 



Beard, 1900, 1902 a, Raja batis, Pris- 



tiurus Reptilia; 



Woods, 1902, Squalus acanthias . Allen, 1906,1907 b, Chrysemysmarginata 



. Jarvis, 1908, Phrynosoma cornutum 

 Teleostomi : 



Nussbaum, 1880, trout Aves: 



Jungersen, 1889, Zoarces viviparus Hoffmann, 1893, twelve species of birds 



Eigenmann, 1891, 1896, Cymatogaster Nussbaum, 1901, chick 



aggre gains 

 Bohi , 1904, trout and salmon 

 Federow, 1907, Salmo fario 

 * Allen, 1909, Amia, Lepidosteus 



A study of the literature shows clearly that there still prevails 

 considerable diversity of opinion about the origin of the cells 

 which afterward become the functional sex-cells. In closely 

 related species, and in some cases in the same species, different 

 observers have reached surprisingly different conclusions. It 

 may be of interest to review briefly the evidence and see wherein 

 the views differ, what they have in common, and so far as possible 

 to reconcile the conflicting opinions. 



The common meeting point is seen at once to be the primordial 

 ova recognized by Waldeyer in the germinal epithelium, forty 

 years ago. Practically all investigators are agreed as to the 

 nature of these cells and their later history. The differences of 

 opinion arise in an attempt to explain their origin. Transforma- 

 tion is the keynote of the germinal epithelium theory and only 

 by actual demonstration of the transformation of peritoneal cells 

 into germ-cells can the theory be established. The literature 

 shows that few writers have actually attempted to show evidence 

 of such a transformation, but have merely assumed that because 

 the earliest observed germ-cells lie among peritoneal cells they 

 arise from them. 



It further appears that of the few who have tried to show such 

 evidence, not a single one has given a good detailed account of the 



