204 A. W. GREENWOOD 



Wilson's Promontory. The first set of testicular and ovarian 

 material was obtained by Professor Agar, who killed and fixed 

 the material. All the other animals obtained were killed and the 

 gonads fixed at the University laboratory. The animals were 

 received at different times during the year, namely in the 

 months of January, April, May, July, and August. In all 

 testis, except those obtained in April, the tubules were filled 

 with various stages in spermatogenesis ; in the latter the 

 tubules contained a relatively large number of Sertoli cells, 

 but other stages in spermatogenesis were few in number. 



Fixing. 



Various methods of fixing the material were employed — 

 Bouin, Allen's modification of Bouin, cold Flemming, and 

 corrosive acetic. The only satisfactory fixatives were the 

 Bouin fluids and the Flemming. For early prophases the 

 Flemming-fixed material gave the best results, but the Bouin 

 fixatives gave very clear figures of the division stages. 



Staining. 



Sections of 10 m and 20 /x were cut. Some were mounted 

 in the ordinary way on glass slides, and others were mounted 

 between coverslips so that the nuclei could be examined from 

 both sides. 



Heidenhain's iron haematoxylin with iron alum was used for 

 staining the sections. Staining with safranin and gentian 

 violet was also tried, but the results were not very satisfactory. 



Number of Chromosomes. 



The diploid number of chromosomes in Phascolarctus 

 is sixteen. This number was obtained from numerous counts 

 in both male and female material. Female counts were obtained 

 from the prophases of large cells of the corpus luteum. One 

 such cell is figured (PI. 15, fig. 1). Altogether sixteen chromo- 

 somes can be seen. In the female it should be noted that no 

 chromatic dot is present, such as is shown so clearly in the 



