CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM 



OF THE OPOSSUM, 



BY J. DUESBERG. 



MATERIAL. 



The object of the present investigation was the study of the chondriosomes 

 and of Golgi's apparatus in the seminal epithelium of the opossum (Didelphys 

 virginiana), the material consisting of nine animals. Five of these were full-grown; 

 a sixth exhibited all stages of spermiogenesis but the very last i. e., the formation 

 of the spiral filament at the expense of the chondriosomes; no spermatozoa were 

 found in the epididymis. The three remaining animals were in a much less advanced 

 stage of development. Whether spermatogenesis in the opossum is taking place 

 throughout the year, or whether the testicle becomes active only before the period 

 of copulation, could not be ascertained, as all the material was procured between 

 August and January. It should be stated, however, that the animals which showed 

 only early stages of spermatogenesis were distinctly smaller than those which had 

 spermatozoa and were probably under one year old. 



In the adult opossum, at least at the time of year when these animals were 

 collected, the testicle exhibits all the characteristic features of a typical mammalian 

 testicle, particularly that striking regularity in the evolution of the germ-cells 

 which was first revealed in the rat. The images are, however, not exactly super- 

 posable, as the duration of the different stages is not the same in both species. I 

 found, for instance, that in the opossum the migration of the ring (which in the rat 

 takes place at the time the cells of the subjacent layer have reached the end of 

 the period of maturation) occurs somewhat later, as the period of maturation is 

 over and the spermatids have already differentiated as far as those represented in 

 figures 17 or 32. 



I was impressed by the large amount of fat that is, such fat as blackens with 

 osmic acid usually present in the seminal epithelium. Fat appears in the seminal 

 cells at the end of the growth period and a number of small fat droplets are con- 

 stantly found in the dividing spermatocytes (fig. 6) and in the young spermatids 

 (fig. 7). It then disappears very quickly and none is to be found after that stage. 

 The bulk of the fat present in the seminal epithelium is contained in the Sertoli 

 cells, and it is here that variations may occur. This fat is apparently a product of 

 the degeneration of the cytoplasm (Regaud's "corps residuel") cast off by the 

 spermatid at the end of its evolution. 



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