362 FREDA M. BACHMANN. 



posterior germ cell is 0.040 mm. posterior to the anus and the 

 germ gland extends 0.160 mm. posterior to the anus. The 

 germinal fold extends only 0.050 mm. anterior to the first germ 

 cell. 



CONCLUSIONS. 



Germ cells in Amiurus nebulosus are distinct from all other 

 cells at least from the time the embryo is 3.2 mm. long. They 

 are then in the lateral plate of the mesoderm. The number of 

 germ cells varies in the different embryos. Until the time when 

 these cells are in or near the germ gland anlage, the average 

 number is 23. With respect to the number of germ cells found 

 on each side the embryo is not symmetrical. When the ccelome 

 is formed they are largely in the splanchnopleure in which they 

 migrate toward the mesentery and in this to the germ gland 

 anlage. There is in most cases no multiplication in number of 

 cells up to the time the germinal fold is formed. The cells 

 migrate into this fold and then divide. There was no transition 

 of peritoneal cells into germ cells observed in any of the stages 

 studied. The epithelial covering and the stroma of the germ 

 gland is derived from peritoneal cells. The germinal fold develops 

 in regions where there are no germ cells. 



This work was done at the university of Wisconsin under the 

 direction of Prof. B. M. Allen, to whom the writer is greatly 

 indebted for the material and for helpful advice and suggestions. 



LITERATURE CITED. 



Bohi, U. 



'04 Beitrage zur Entwickelungsgeschichte der Leibeshohle und der Genitalan- 



lage bei den Salmoniden. Morph. Jahrb., 32, 1904. 

 Dodds, Gideon S. 



'10 Segregation of the Germ Cells of the Teleost, Lophius. Journ. Morph., 21 : 



563-595. 1910. 

 Eigenmann, C. H. 



'92 On the Precocious Segregation of the Sex Cells in Micrometrus aggregatus. 



Journ. Mroph., 5: 481-493. 1892. 

 '96 Sex Differentiation of the Viviparous Teleost Cymatogaster. Arch. f. 



Entwickelungsmechanick, 4: 125-179, 1896. 

 Hoffmann, C. K. 



'86 Zur Entwickelungsgeschichte der Urogenitalorgane bei den Anamnia. 

 Zeitschr. f. wiss. Zool., 44: 570-644, 1886. 



