174 VOL UTION AND DISEASE. 



As all cutaneous recesses exhibit a marked tendency 

 to develop glands, the large size and abundance of the 

 mammary glands within the marsupium of opossums 

 receives an explanation. 



A comparison of the inguinal pouches in the sheep 



FIG. 92. The marsupium of a Phalanger (Phalangista orientalis) 

 opened to show the number of teats. 



with the marsupium of the phalangers, &c., is instructive, 

 as it indicates in a significant manner the mode by which 

 a specialized bag, or marsupium, may have originated, 

 besides throwing light on the number of teats it con- 

 tains. 



