16 Papers from the Marine Biological Laboratory at Tortugas. 
of Washington and particularly Dr. Alfred G. Mayer, director of the Marine 
Biological Laboratory at Dry Tortugas. 
The testes were fixed in sublimate acetic and Flemming’s strong fluid, 
both methods yielding beautifully preserved specimens. Heidenhain’s iron- 
hematoxylin long method was employed almost exclusively, both with and 
without counterstaining. The various structures were studied in the light 
of their morphology rather than their staining reaction and always at the 
stage of moderate decolorization. However, methyl green and thionin were 
also employed and confirmed in every detail (except in the case of the 
ripe spermatozoon, to be noted later) the results of the morphological study 
in the hematoxylin-stained sections. The sections were cut at 6.67 micra. 
OBSERVATIONS. 
The testes are paired and consist of two long thin-walled follicles which 
extend for a considerable distance on either side of the abdomen. Each 
contains a ventral collecting duct which is continuous with a vas deferens. 
The follicles are composed of many cysts. Spermatozoa are found in large 
numbers in the proximal (posterior) end of the collecting duct ; immediately 
surrounding this area is the zone of spermatids; then appear the spermato- 
cytes, and then, when present, the secondary and primary spermatogonia. 
Usually only the later stages are present in the proximal end of the testis 
and only the earlier in the distal end. 
PRIMARY SPERMATOGONIUM. 
The follicular wall consists of large flattened cells with elongate vesicular 
nuclei. This wall is continuous with the wall of the vas deferens, as well as 
with that of the numerous cysts. Except at the proximal end the follicular 
wall appears to be two cells in thickness. The inner cells are large and 
polyhedcal, with very large oval vesicular nuclei, the wall of which is fre- 
quently lobed (fig. 2), and with a small amount of cytoplasm. These are 
the primary spermatogonial cells in the resting stage (fig. 4). At the 
distal end of the follicle, primary spermatogonia are abundant and the two- 
layered condition of the wall is not apparent. Nuclei of the cyst-walls are 
essentially similar to those of the primary spermatogonial and follicular cells. 
They vary in size between the latter cells, are vesicular, frequently lobed, and 
contain a delicate reticulum with occasional karyosomes (fig. 3). Neither of 
these nuclei contain a plasmosome. There are unmistakable signs of amitotic 
division among the primary spermatogonial cells next the follicular wall 
resulting in binuclear or polynuclear cells (fig. 1). Less convincing evidence 
of amitosis appear also among the nuclei of the follicular and cyst-walls. 
All three types of cells are frequently seen in karyokinesis and the process 
appears identical in each. The close similarity of nuclear structure and 
nuclear changes during division among the three types of cells forces the 
conclusion that they are identical. 
