CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 63 



help expressing (1912) great skepticism, which the results of my present investiga- 

 tions entirely justify. The main conclusion reached, in fact, is that there is no 

 discontinuity in the chondriosomes of the seminal cells in the opossum. Chondrio- 

 somes are present at all stages of spermatogenesis from the spermatogonia and the 

 Sertoli cells to the ripe spermatozoa. This conclusion, arrived at through the study 

 of the adult testicle, is corroborated by the study of the organ in young animals. 

 I come now to the details of my observations. 



SERTOLI CELLS. 



Chondriosomes are exceedingly numerous in the Sertoli cells (fig. 1) and exhibit 

 a marked resistance to destructive influences, including the action of acetic acid. 

 One can obtain preparations in which most of the chondriosomes, especially in the 

 early stages of spermatogenesis, are destroyed, while they are preserved in the 

 Sertoli cells. In such preparations the cell-body, with its processes, is sharply 

 brought into evidence. The nucleus is very darkly staining and, as in other mam- 

 mals, shows indentations. Droplets of fat, blackened by osmic acid, are very 

 numerous at certain stages, namely, immediately after the resorption of the resi- 

 dual bodies. The chondriosomes are either granules or filaments. Some of these 

 latter are very long and may extend into the processes, but are usually confined to 

 the basal part of the cell, around the nucleus. 



SPERMATOGONIA. 



The resting spermatogonium (fig. 2) flattened against the basal membrane, 

 contains, besides a relatively large nucleus, an idiozome and, notwithstanding 

 Jordan's assertion to the contrary, numerous chondriosomes, but no fat. The 

 chondriosomes are all mitochondria, massed wherever they find space, mostly at 

 the poles of the nucleus. The idiozome is usually hidden by them. During mitosis 

 the cell rounds out and the mitochondria are found at the metaphase (fig. 3) scat- 

 tered all around the spindle, and later between the daughter-nuclei. 



SPERMATOCYTES. 



During the first phase of the growth period the chondriosomes keep their 

 granular form. They are gathered mostly around the idiozome at one pole of the 

 nucleus (fig. 4) . Jordan denies the existence of such a distribution, because, having 

 overlooked the chondriosomes in this stage he endeavored to find the same condi- 

 tion when it no longer existed. As a matter of fact, this distribution of the chon- 

 driosomes is of common occurrence in the first phase of the growth period in mam- 

 mals. Later on the location of the chondriosomes changes and they are found all 

 around the nucleus (fig. 5). Their shape likewise is modified; most of them are now 

 short, rather thin filaments, retaining this form well into the period of spermio- 

 genesis. They never look like the dumb-bells represented by Jordan in figure 24, 

 nor like the granules in his figures 25, 26, 27, 29, 30, 31, 32, 33, 34, 36, 37, and 38. 

 Nor are they located in the cell as his chromidia shown in the same figures. As to 

 the metachromatic granules, "which are tentatively interpreted as the earlier 



