Marsupial Spermatogenesis. 



By 

 A. W. Greenwood, B.Sc, 



University of Melbourne. 



With Plates 15 and 16, 



Introduction. 



This work is a contribution to the cytology of the Marsupials, 

 a group which, owing to the small number of their chromosomes, 

 affords peculiar advantages over other mammals for this 

 kind of study. The sex chromosomes are particularly clear in 

 this group, and Painter's discovery of a Y-chromosome in the 

 American opossum (Didelphys) has been fully confirmed 

 in several 'species of Australian Marsupials examined in this 

 laboratory. In the present paper I give the results of the 

 study of three species of Marsupials belonging to two different 

 families, two species belonging to the family Dasyuridae of the 

 sub-order Polyprotodontia, and one to the family Phalan- 

 geridae of the sub-order Diprotodontia. 



The form examined in most detail is Phascolarctus 

 cinereus. In the other forms I have done little more than 

 determine the number and the behaviour of the sex chromo- 

 somes. 



The following work was undertaken under the guidance, 

 and with the assistance, of W. E. Agar, F.E.S., Professor of 

 Zoology in the University of Melbourne. 



Spermatogenesis of Phascolarctus cinereus. 



Material. 

 The animals were obtained through the courtesy of Mr. Ker- 

 shaw of the National Museum, from the National Park at 



