68 CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 



As clearly shown in figures 15a and 16, there is a great discrepancy between the 

 size of the chondriosomes and the thickness of the spiral after Benda's fixation. 

 I do not doubt that the appearance represented in figure 15a is somewhat artificial 

 and due to a certain amount of swelling. Certainly the chondriosomes after 

 Regaud's fixation are more similar in form to those in the living cell than they are 

 after Benda's fixation. 



The formation of the spiral filament at the expense of the chondriosomes, in 

 the spermatozoon of marsupials, was first described by Benda (1897) for Phalan- 

 gista. Von Korff came to the same conclusion both for Phalangista and Didelphys; 

 it must be stated, however, that his representation of the spiral filament in the last- 

 named species (text-figure 3) is somewhat schematic. In a later paper Benda 

 (1906) confirms his former description for several marsupials. Jordan also has 

 observed the spiral in the opossum. Finally, in the present paper I have followed 

 its formation, step by step. In fact, it is such a conspicuous constituent of the 

 spermatozoon that it is hard to understand how Retzius failed to see it. That 

 author has published two papers on the spermatozoon of marsupials. In 1906 he 

 studied Bettongia cuniculus, Macropus billiardieri, Petrogale penicillata, Onycho- 

 gale lunata, and Phalangista vulpina. The structure of the middle piece is in all 

 these species the same; it is covered by a relatively small number of rather large 

 granules, disposed in longitudinal rows. For Phalangista Retzius expressly states 

 that the regular disposition of the granules simulates a cross-striation, but he fails 

 to compare his results with the entirely different ones of Benda and von Korff, 

 although he mentions them. The next paper (1909) deals exclusively with Didel- 

 phys. Here again the middle piece is found covered with granules: 



"Diese Korner liegen in geraden Reihen, mit zehn Kornern in jeder Langsreihe; von 

 der Seite betrachtet zeigt das Verbindungsstiick drei solche Langsreihen. Nach dieser 



Berechnung dtirfte die Anzahl der Korner sich auf etwa 40 belaufen Sie liegen 



auch am reifen Spermium nicht in spiraliger Ordnung, sondern regelmassig der Quere 

 nach, und sie verwandeln sich jedenfalls nicht zu einer Spiralfaser. (p. 125)." 



I disagree with this description, first, in the estimate of the number of rows; 

 second, as to the form of the chondriosomal sheath of the ripe spermatozoon, where, 

 like Benda, von Korff, and Jordan, I found a spiral filament. This difference might 

 be explained in two ways: First, the species studied by Retzius may not have been 

 Didelphys virginiana; this hypothesis, however, is rather improbable and would 

 not account for the discrepancy between his conclusions and those of von Korff 

 and Benda concerning Phalangista. The second hypothesis, which would explain 

 all differences, is that the material studied by Retzius was poorly preserved and 

 showed a chondriosomal sheath that had fallen to pieces. 



While writing on the structure of the mammalian spermatozoon I wish to 

 correct certain errors appearing in the second edition of Bonnet's Embryology 

 (1912, p. 28), in the reproduction of some of my drawings showing the development 

 of the spermatozoon of the guinea-pig (1910). What Bonnet calls "vordere Hals- 

 knotchen" in figures d and e, is really the posterior edge of the headcap; while his 

 "hintere Halsknotchen" are the fragments of the proximal centriole and should be 



