CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 01 



head and the so-called "copulation" of the spermatozoa. The first phenomenon is 

 described by von Korff (p. 254) as follows: 



"Der Schwanz der Spermie liegt vor der Kopulation zweier Spermienkopfe quer zu 

 den beiden Schenkeln, nach derselben dagegen langs zu ihnen und zwar mit dem vorderen 

 conischen Ende des Verbindungsstiickes und dem Halse zwischen ihnen." 



The copulation of two spermatozoa was first described by Selenka. Von Korff 

 observed it in Didelphys but not in Phalangista. However, as Selenka states that 

 most of the spermatozoa found in the vagina of Phalangista are twin cells, von 

 Korff suggests that the copulation may take place only after the passage of the 

 spermatozoa in the epididymis; i. e., in the vas deferens. Retzius (1906) does not 

 mention the presence of twin spermatozoa in Phalangisla, but found them in the 

 epididymis of Didelphys (1909). Jordan apparently overlooked them at first (p. 54), 

 but corrected his opinion afterward (note 4, p. 76) . I myself also found the copu- 

 lating spermatozoa in the epididymis of the opossum. Preparations fixed with 

 osmic acid and stained with Benda's method show that a distinct line of demar- 

 cation between the two heads is visible only in the posterior part (fig. 25). The 

 fusion is, however, not as intimate as this appearance would lead one to believe; 

 indeed the connection must be a rather loose one, as in smears the spermatozoa are 

 often found separated. As to the significance of the copulation nothing is known. 

 Some clue might be expected from a study of the fertilization in Didelphys; unfor- 

 tunately, in Hartmann's paper on the subject (1916) the fact is not even mentioned. 



A description of the complicated head of the spermatozoon has been given by 

 von Korff (p. 254) and by Retzius (1909). One detail of structure has apparently 

 been overlooked by von Korff, but is described by Retzius. This author mentions 

 the presence, in close proximity to the insertion of the tail, of 



"einer kleinen, bei der Osmium-Rosanilin-behandlung rot, nach der Sublimat-Hama- 

 toxylinalaun schwarz farbaren Kugel, welche offenbar einem Centralkorper entspricht. 

 Nach der Ablosung des Schwanzes nebst dieser Kugel bleibt gewohnlich ein heller Fleck 

 an der Scheibe zuriick, welcher wohl als ein Griibchen aufzufassen ist, in welchem die 

 genannte Kugel angeheftet gewesen ist." 



No such structure could be found after Benda's stain (cf. figures on plate 1, 

 and fig. 25), but it was brought into evidence after osmic fixation by iron hema- 

 toxylin (fig. D), and by acid fuchsin-methyl green after Fio.o.-Theheadsoftwo 



fixation with Regaud's fluid (figs, 18, 19, 20, 22, 23, copulating .permato- 



H (S) n zoa ' a sectlon of 



and 24). As the latter series shows, the structure ^AlM the epididymis, stained 



, . ,. ., i -okj i with iron-hematoxylin 



appears during the development ol the spermatozoon, VjL/ after Benda ' s fix^m,,. 

 and is always to be found on the thick branch of the 



nucleus; i. e., the one through which the twin spermatozoa become united (figs. 18, 

 19, 20, 22, 23, 24, and D). 1 never saw any evidence of the presence of a granule 

 in this depression, as accepted by Retzius, and while I would leave this point un- 

 decided one thing is certain : If such a granule exists it has nothing to do with the 

 centrioles. 



The centriolar ring, or "Schlusscheibe," is described by Meves (1899, p. 360, 

 footnote) and pictured by von Korff (text-figures 3 and 4) and by Retzius (1909, 



