356 FREDA M. BACHMANN. 



that before any differences between germ cells and somatic 

 cells can be detected there must be an unseen physiological dif- 

 ference which determines the future behavior of the cells. 



The eggs of Amiurus nebulosus vary in size in the different 

 nests. There is often a difference of I mm. in diameter. For 

 this reason it follows that embryos of the same length are not 

 necessarily of the same stage of development. Embryos 3.2 

 mm. long taken from one nest may be slightly further developed 

 than those 3.7 mm. long taken from another nest. 



When stained with iron hematoxylin the yolk granules of the 

 egg are black but if this is washed out with iron alum and then 

 followed by congo red the granules are a deep red. The yolk 

 material in the germ cells is more or less diffused through the 

 cytoplasm and loses the black hematoxylin stain quite readily 

 in the iron alum. But because of the contained yolk the cyto- 

 plasm of the germ cells stains a deeper red than the cytoplasm 

 of the surrounding cells. Occasionally there is a small compact 

 mass of yolk in a germ cell which retains the black stain. Yolk 

 granules of the egg stain lightly with Mayer's haemalum but 

 take up the Orange G very rapidly. Hence the cytoplasm of 

 the germ cells stains a light orange with haemalum and Orange G. 

 The cytoplasm of the surrounding cells is a bluish gray. 



The germ cells in all of the stages studied up to the time of 

 multiplication were found to be about the same size. They are 

 from 14 to 1 8 microns in diameter and the nuclei 7 to 9 microns 

 in diameter. The germ cells are quite well rounded though 

 sometimes they are more or less amoeboid. The cytoplasm is 

 quite clear, especially so if the contained yolk is in one or two 

 compact masses. The nucleus is spherical or frequently lobed. 

 But this lobed condition of the nucleus is not peculiar to the 

 nuclei of germ cells it is often found in nuclei of other cells. 

 There are often two nucleoles but again this is no peculiarity of 

 germ cell nuclei. In the very early stages of development most 

 of the somatic cells have more than one nucleole and two nucleoles 

 are seen in the nuclei of many somatic cells long after the ccelomic 

 cavity is formed. Not infrequently there are no nucleoles 

 in the germ cell nuclei. The chromatin which is fairly distinct 

 is scattered through the nucleus in the form of fine granules. It 



