CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 55 



ered as a secretion of this last body "on its surface furthest from the nucleus," as 

 the two parts are already differentiated in the perfectly spherical acrosome before 

 its connection with the nucleus. I refer to Meves's figure 9, and to Moore and 

 Walker's figures 39, 40, and 41, and would call attention to the fact that Meves 

 insists (pages 344 and 389) that this is not an appearance due to extracting the stain 

 more or less, as both parts can be distinguished in unstained preparations. Finally, 

 concerning the vacuolar structure of the outer part of the acrosome, I consider the 

 point of little importance, as its appearance varies considerably according to the 

 fixing reagents and type of stain used. (See for example figs. 61-68, Duesberg 1910.) 

 I come now to my own observations on the opossum and hasten to declare 

 that I have little to say here in regard to the spermatogonia and the sperma- 

 tocytes. Their nuclei I did not study, and their cytoplasmic constituents will be 

 described in the following chapters. Concerning the first spermatocytes I would 

 only mention that again, as in the rat, guinea-pig, and cat (Duesberg, 1910, p. 66), 

 the growth period can be divided into two phases: 



"Dont Tune va jusqu'a la formation des grosses travees chromatiques, tandis que 

 1'autre est posterieure a ce stade. Au cours de la premiere phase, le spermatocyte de premier 

 ordre est tres petit et s'accroit relative ment peu. Pendant la seconde, protoplasme et 

 noyau augmentent fortement de volume, Faugmentation de volume du noyau etant par- 

 ticulierement remarquable chez le rat. II y a done ici quelque chose de comparable a ce qui 

 se passe an cours de la periode d'accroissement de la cellule sexuelle femelle, la seconde phase 

 correspondant a la periode dite du grand accroissement (Gregoire, 1908) de 1'ovule." 



Mention should be made also of the idiozome as it appears after the action of 

 reagents containing osmic acid. This body consists of two parts, an outer, darkly- 

 staining shell, and a lighter medullar substance. In the spermatogonia and in the 

 young spermatocytes it is usually flattened against the nucleus, and in prepara- 

 tions in which the chondriosomes are preserved it is often entirely covered by 

 these bodies (figs. 2 and 4). In the older spermatocytes the idiozome rounds out 

 and then it is clearly apparent that the outer shell is missing opposite the nucleus 

 (fig. 5). In the dividing spermatocytes it can be occasionally recognized as late as 

 the metaphase, after which it falls to pieces. What becomes of these pieces is 

 difficult to determine without the application of special methods. (See chapter 

 on apparatus of Golgi). 



Concerning spermiogenesis I would say that no attempt was made to describe 

 the process in every detail. The study was undertaken in order to build on a safe 

 foundation my researches on the chondriosomes and the apparatus of Golgi. I 

 would also add that I was handicapped, especially in the study of the centrioles, by 

 the lack of good iron-hematoxylin preparations. Enough could be elucidated, 

 however, to make it appear worth publishing. As to the subdivision of the process, 

 my experience was similar to that of von Korff, and like him I have to adopt the 

 modifications of the centrioles as a basis. 



FIRST PERIOD. 



The young spermatid (fig. 7) contains, in addition to the chondriosomes with 

 which I shall deal later, a spherical nucleus, an idiozome, and two granular centrioles 



