594 Gideon S. Dodds. 



with the ingestion by particular cells of the granules of the pole- 

 disc. Rather less complete descriptions of a similar process in 

 some other insects had been given by earlier writers and mentioned 

 by Hegner. Wieman ('09) studied the origin of the pole-disc in 

 Chrysomelid eggs and found that the granules are secreted by 

 the nurse cells and that the pole-disc is a portion of them which 

 did not become transformed into yolk. 



Among the preceding cases of very noticeable nuclear changes 

 at the time of the segregation of the germ-cells there is no appar- 

 ent uniformity between the different species but the relation of 

 these different processes to the first segregation of the germ-cells 

 is clear. In the light of these cases it is not surprising that in 

 Lophius we should find nuclear changes of still a different sort. 

 The extrusion of plasmosome material from the resting nucleus 

 of the germ-cells of Lophius is an example among vertebrates of 

 a process resembling the changes known to take place at the time 

 of their segregation in a number of invertebrates. 



Summary 



The separation of somatic- and germ-cells is one of the early 

 differentiations in the segmenting egg of Lophius. 



It has not been possible to recognize the germ-cells during the 

 earliest stages of this process, but there is no question that the 

 process is completed before the beginning of embryo formation. 



The first clearly recognized germ-cells lie in the primary ento- 

 blast at a stage when the blastoderm has not quite half covered 

 the yolk and the formation of the embryo has but begun. 



The germ-cells pass into the mesoblast during its separation, 

 or shortly thereafter. 



The 'period of rest ' of the germ-cells begins before the separ- 

 ation of the mesoblast and continues until after hatching. It 

 corresponds to the period of 'embryo formation.' 



The observations on Lophius do not cover the earlier period 

 of multiplication of the germ-cells. The apparent increase during 

 certain early stages, is due to changes in the germ-cells which 

 make them recognizable. 



