GIO THE ORGAN OF JACOBSON IN MARSUPIALS, 



of Fetrogale pe^iicillata, and found that the condition in Ijoth 

 forms is " practically identical." Of this group I have examined 

 (1) a series of sections prepared by Prof. Wilson, of a very small 

 mammaiy fcetus of Macropus spJ ; (2) a large mammary foetus of 

 M. ualabatus; and (3) a small mammary fcetus of ^Epyprymnus 

 rufescens. 



Sub-family Macropodin^. Plate (xlvii. figs. 1-9.) 



Macropus s]).? (mammary foetus, total length 29 mm.). In this 

 very young foetus the condition of parts agrees very closely with 

 that in Trichosurus. The nasal-floor cartilage is well developed 

 in the anterior part (PL xlvii. fig. 1), but before reaching the upper 

 opening of the naso-palatine canal the outer part is lost. There 

 is a distinct though small downward process. The nasopalatine 

 canal passes up almost vertically, and the organ of Jacobson 

 opens into it on the same plane as that in which it unites with 

 the nasal cavity (fig. 2). The palatine process is I'epresented as 

 in Trichosurus by an ossifying rod near the middle of the inner 

 plate of Jacobson's cartilage. Posteriorly the condition agrees 

 with that in the early ftetal Trichosurus. 



Macropus ualabahis, Less. & Garn., (large mammary fcetus 

 head 50 mm.). This specimen may be taken as the tj'pe of the 

 Kangaroo. 



In front of the naso-palatine canal (PI. xlvii. fig. 3) the nasal- 

 floor cartilage is rather feebly developed and very simple in 

 structure. There is no distinct septal ridge, and in consequence 

 the inner end of the floor cartilage remains more simple than in 

 the Phalangers. Inferiorly a broad papillary cartilage is seen. 

 In fig. 4, where the naso-palatine canal begins to be seen, the 

 nasal-floor cartilage becomes very much thickened and dips down 

 in the hollow formed where the palatine process is about to divide 

 off from the premaxilla. The condition resembles in general 

 appearance that of Phascolarctus more than that of the Phalan- 

 gers. On reaching the plane where the palatine process becomes 

 quite distinct from the premaxilla the following condition is seen 

 on section (PI. xlvii. fig. 6). The lai-ge dipping down portion of 



