MIGRATION OF GERM CELLS IN AMIURUS NEBULOSUS. 36! 



were sectioned the germ cells had found their way into the peri- 

 toneal fold. The number remains the same 28 to 30. The 

 size and appearance of the cells agree exactly with the same in 

 the earliest stages. The germ cells are distributed throughout 

 a distance of 0.980 to 1.020 mm. The most posterior cells are 

 0.420 to 0.520 mm. anterior to the anus. It will be seen that 

 although the embryos have increased much in size, the length 

 throughout which the germ cells are distributed in proportion 

 to the length of the embryo is about the same. 



EMBRYOS 14 MM. LONG. 



In all of the embryos of this stage the germ cells had divided 

 at least twice. There had probably been two divisions in one 

 embryo where the number was 144. Here the germ cells measure 

 812 microns in diameter and the nuclei are 4-6 microns. The 

 chromatin is no longer in such fine granules as in the early stages 

 but is often aggregated into small masses. The germ cells are 

 in the center in the peritoneal fold with strands of peritoneal 

 cells between them (Fig. 10). There is nothing which would 

 suggest a differentiation of peritoneal cells into germ cells. 

 Some of the germ cells are smaller than others but it is believed 

 that these are cells which have divided more times than the larger 

 ones and not that they are transition cells (see Fig. 10). No 

 germ cells were found as large as even the smallest of those in 

 younger stages. The germ cells and peritoneal cells stain as 

 distinctly different as described before and no cells intermediate 

 in size or staining qualities were found. In this embryo of 144 

 germ cells the germ gland or fold extends only o.oio mm. anterior 

 to the first germ cell but 0.500 mm. posterior from the most 

 posterior germ cell. The germ cells were distributed throughout 

 a distance of 1.280 mm. and the germinal fold throughout 1.790 

 mm. 



In another embryo of the same length the germ cells had 

 evidently divided several times the cells here were only 6 or 7 

 microns in diameter and the nuclei about 34 in diameter. There 

 are twenty or more germ cells in every section of each of the 

 glands. The cells were not counted in the entire embryo. They 

 are distributed throughout a distance of 1.220 mm. The most 



