THE SPERMATOGENESIS OF UMBRA LIMI. 133 



and attributes the formation of the early spermatogonia to cells 

 which migrate into the testes from a cord of germ cells outside. 

 Geiser ('24) says: 'The definite sex-cells by repeated divisions 

 give rise to the final spermatogonia .... The cysts of sperma- 

 togonia are the result of the continued fission of the germ-cells 

 which at the season of sexual activity migrate to the periphery of 

 the gonad." A recent article on the origin of the germ-cells in 

 the adult salamander is of special interest here. Hargitt ('24), 

 working on the salamander (Diemyctylus mridescens] shows that 

 the cysts do not retain residual spermatogonia, but the new 

 crop of spermatogonia is formed each season from migrating 

 cells of the peritoneal covering of the testis or from the epithelial 

 lining of the collecting ducts. Hargitt found isolated nests of 

 germ-cells in the mesenteries and peritoneum outside the testis 

 but he does not attribute the origin of the new spermatogonia in 

 old cysts to these cells. From his observations on the behavior of 

 the germ-cells in the testis of Umbra the writer is led to believe 

 that, as in the perch (Turner, '19), and in the salamander 

 (Hargitt, '24), the primary spermatogonia are formed anew each 

 season from cells which migrate from some point outside the 

 lobules and possibly outside the testis. No cords of germ-cells 

 were found outside the testis of Umbra, however, as described 

 for the perch by Turner. The evidence points more to some 

 such type of origin as that described by Hargitt for the sala- 

 mander. 



I find the seasonal cycle in Umbra to coincide in the main 

 with that found in the perch by Turner ('19). Two distinct 

 differences might be pointed out : (i) Beginning with the multipli- 

 cation period the spermatogenetic cycle in Umbra is more rapid 

 than that found in the perch. (2) The writer believes the 

 migration of the new germ-cells to be a continuous process in 

 Umbra though slower at some times than at others, instead of 

 being restricted to any one particular period as was found in 

 the perch. 



The growth phase of the primary spermatogonia varies in 

 different fishes. Turner ('19) working on the perch, and Geiser 

 ('24), working on the top-minnow (Gambusia), found a definite 

 growth period. In the perch the primary spermatogonia are 



