588 Gideon S. Dodds. 



suppose, as suggested by Allen ('06), that slow movement of 

 germ-cells among cells of surrounding tissues may be accom- 

 plished by slight movements, not sufficient to give distinct amoe- 

 boid shape. 



b. Path of migration. The path followed by germ-cells in their 

 migration to the genital ridge has been described somewhat dif- 

 ferently for each species studied. These differences, however, are 

 but variations of the same general course. In Lophius, but one 

 feature of the migration seems worthy of comment — at one stage 

 all of the germ-cells are found in the myotome. When I first saw 

 them in this part of the embryo, I thought possibly there was a 

 mistake about their identity, because, at this stage it is no easy 

 matter to recognize them. Study of several embryos of stage 

 6, 7 and 8, however, showed that these were really germ-cells, 

 and that in some embryos none could be found in any part of the 

 body except in the myotome. It showed also that the natural 

 path of migration was through the myotome (cf . figs. 2-5) . 



The writer does not attach any special importance to this fea- 

 ture of the migration path in Lophius. It does not seem to make 

 any difference what parts of the embryo are traversed in the migra- 

 tion nor in what parts of the body they may find temporary lodg- 

 ment. The path varies in different animals, but in each species 

 it is fixed and definite. 



The question why they follow a definite path in one species and 

 a somewhat different one in another cannot at present be answered 

 in full. The details of the path seem in some way to be correlated 

 with the course of development of the embryo, but the exact 

 relations do not appear" very clear. It might be expected that 

 the path of migration would be the shortest and most direct 

 course to the place to be reached. The course does not, however, 

 appear to be determined in this way, and in Lophius shows several 

 deviations which cannot be accounted for by such a simple explan- 

 ation. We see the first possiblility of comphcations when we 

 note that the migration is in part due to the cells themselves 

 and in part to the tissues of the embryo. 



c. Segmental relations. It is of interest to inquire whether at 

 any time, in Lophius, the arrangement of the germ-cells is seg- 



