576 Gideon S.- Dodds. 



The ventral mesentery, however, is of very short duration. At 

 this stage, all of the germ-cells are located at the base of the 

 mesentery where they are more closely aggregated than in stage 

 13 (fig. 11). A study of stages a little younger than this, shows 

 that the germ-cells are, in large part, pulled into position at the 

 base of the mesentery by the folding of the coelomic wall which 

 forms the mesentery. It seems probable, however, that there is 

 also at this time an active migration of the germ-cells themselves 

 to bring about their closer grouping. 



The germ-cells are now in the position of the permanent germ- 

 glands (ovary or testis) and the studies on Lophius were not car- 

 ried beyond this point. The studies of Eigenmann ('96) and 

 Bohi ('04), on other Teleosts, show clearly enough the fate 

 of these cells. These writers have traced them in the gonads 

 up to the time of sex differentiation and have found that the 

 functional sex-cells arise as their lineal descendants. 



In the foregoing account we have traced the germ-cells from 

 their position in the primary entoblast, where they were first 

 distinguished, till they have reached the place of formation of the 

 gonads. It should be borne in mind, however, that this study 

 does not assume to show the actual origin of the germ-cells in 

 Lophius. This account simply takes up the history from the 

 time at which I was first able to recognize them. Reasons will 

 be given later, for believing that they are set apart at a time 

 earlier still in embryonic history. 



There remains yet to be described, the antero-posterior dis- 

 tribution of the germ-cells. Some idea of this may be had by 

 reference to figs. 12-18, where the actual number of germ-cells 

 and their position are indicated by black dots upon outline draw- 

 ings of the embryos. Each drawing pictures their actual position 

 in a single embryo. To determine their distribution, a camera 

 lucida drawing was made of each section in which germ-cells were 

 found. The position of each cell was then plotted according to 

 the section in which it was found. From a study of twelve 

 embryos it is quite evident that the arrangement of the germ- 

 cells is not alike in any two embryos of the same age so that 

 groupings very different from those figured are found, though as 



