122 JAMES O. FOLEV. 



remain over as suggested, or they may degenerate. No positive 

 evidence can be presented on this point although similar large 

 cells, showing occasional mitosis, can be observed throughout 

 the time that the testes are filled with spermatozoa. 



The origin of the early spermatogonia can be best observed 

 just before the liberation of the spermatozoa. At this time the 

 new germ-cells, which are to be found around the periphery of 

 the lobule, are of varying sizes, ranging from small migrating 

 cells (Fig. i) to very large cells (Fig. 2) in a growing or resting 

 condition. Of twenty-four linear measurements taken at random, 

 cells were found to range from 19.50 to 58.50 micra. The 

 migrating cells (Fig. i) are ameboid in shape and have a darkly 

 staining nucleus with a thin investing sheath of cytoplasm 

 closely applied to the nuclear membrane. The nuclei take the 

 stains more deeply than the nuclei of the large resting cells in the 

 same lobule. The migrating cells (Fig. i) are oblong or flattened 

 with a prominent chromatin nucleolus suspended in the nuclear 

 reticulum near the nuclear membrane. The chromatin granules 

 are quite large and peripherally arranged around the nuclear 

 membrane. 



2. Growth of the Spermatogonia. As soon as the migrating 

 germ cells become lodged at the periphery of the lobule the 

 growth period of the spermatogonia begins. This growth period 

 is of special interest in Umbra and other Teleosts for in these 

 forms the great increase in cell size during spermatogenesis is 

 thrown back into the early spermatogonial stages. In most 

 animals the growth period occurs in the primary spermatocyte 

 stage and it is usual to find the spermatogonia of almost equal 

 size. The precocious growth period of Teleosts may be due to 

 a number of factors: (i) All the spermatogonia formed during 

 any one season are ultimately used up. (2) The method of cyst- 

 formation in tin- lobule, in which each migrated germ-cell becomes 

 the primary center of a cyst; since each seasonal crop of germ- 

 cells arises anew from migrating cells. (3) The long period of 

 rest in the testis following its depletion of spermatozoa, during 

 which time there is an active reorganization of the testis itself 

 conditioned by the constant arrival of new germ-cells from some 

 point outside the lobule. (4) The shortness of the time between 



