360 



the external characters of pouch embryos of 

 Marsupials. 



no. ^-trichosurus vulrecula. var. typicus. 



By F. Wood Jones, D.Sc, F.Z.S., 

 Professor of Anatomy in the University of Adelaide. 



[Read October 14, 1920.] 



Plates XIV. and XV. 



Introductory. 



The necessity for recording all details concerning the 



Australian mammalian fauna needs no emphasis. No one 

 acquainted with the conditions prevailing in Australia to-day 

 will dispute the fact that the marsupial fauna is a rapidly 

 dying one, and no systematic zoologist will deny that current 

 descriptions, written very often from dried museum skins, 

 may well be amplified by the inclusion of charts of hair 

 tracts, etc., which can only be done with advantage in the 

 pouch young. The amount of fresh or well-preserved material 

 is comparatively limited, and it is highly desirable that 

 descriptions of such material as is available should be made 

 accessible, while it is still possible to deal with adequate series 

 of any given type. From time to time pouch embryos and 

 fresh and spirit-preserved adult material are (as a generous 

 response to correspondence) coming under the observation of 

 the writer. It has been deemed important that before any 

 of this material is subjected to anatomical investigation, either 

 gross or microscopic, it should be dealt with from the com- 

 paratively uninteresting, but nevertheless important point of 

 view of the systematist, who is concerned in the main with 

 the more striking features of gross external anatomy. 

 Following this maxim, the writer has adopted the plan of 

 recording, in the form of notes, drawings, and photographs, 

 all material submitted to him. The completeness of these 

 records, rather than the systematic position of the animal, 

 must determine the order in which material is prepared for 

 publication. Expediency demands this method. But its 

 disadvantages are at once obvious. In the first place, until 

 the whole series of descriptive papers is collected and cor- 

 related, any consecutive ideas of the interrelations of types 

 will be difficult to come by. In the second place, a oreat 

 amount of duplication of work must be done, since contrasts 

 between, and comparisons with, other types will be practically 



