774 ANATOMY OF VERTEBRATES. 



tint, each 3J grains in weight, and 8-10ths of an inch in length 

 to the end of the tail : adhering strongly to the nipple, suck- 

 ing actively, and clinging to the fur by the unguiculate digits of 

 their fore-limbs, which they used freely. One survived separation 

 from the nipple one hour and twenty-nine minutes, turned itself 

 over and moved round the glass in various directions : respiring 

 by the nostrils twenty-two times per minute, and ejecting bubbles 

 of milk from mouth. The hind-limbs were each a mere bud, 

 with feeble indications of toes, without claws. The tongue is very 

 large — J the entire weight of the head. The power of suction 

 is such that the point of a pencil applied to the oral pore is held 

 so strongly that the young can be partially lifted up by it. On 

 March 14th the young weighed 12 grains, showing an increase 

 of weight at the rate of 250 per cent, in seven days : it was now 

 1 t 1 q inch long. On March 18th the weight was 18 grains: the 

 claws appeared on the hind-toes : the testes had descended into 

 a large scrotum. The eyelids were still sealed, but movements 

 of the eyeball were visible beneath the skin. On May 22nd 

 Dr. Meigs found one of the young crawling on the body of the 

 dam ; its weight was 42 grains ; the eyes were open. This gave 

 a term of marsupial gestation of 74 days. But the young return 

 to the pouch for food and shelter until near the time for reception 

 of a succeeding litter. 



In Thylacinus the pouch opens backward, or vent-ward, as in 

 Perameles ; and shows four nipples. 1 In a female which carried 

 there three young, each 1 foot in length from the snout to the 

 end of the tail, the length of the pouch was 8 inches ; its aperture 

 was 3 J inches wide, and the bag expanded as it extended forward to 

 a width of 6 inches. The teats were 4 inches long. The young 

 were males : the testes had descended into a pendulous scrotum one 

 inch in advance of the cloaca, from which the grooved but undivided 

 penis projected : the eyelids were closed, but not adherent. The 

 tongue presented a longitudinal rising, with a medial groove, the 

 rising fitted into a depression on the roof of the mouth bounded 

 by two, parallel, long and narrow palatal bones, recalling the con- 

 dition of these bones in Sauria. In Myrmecobius ' the female is 

 destitute of a pouch and has, apparently, eight nipples, arranged 

 in a circle.' 2 



Besides the natural and portable nest, some Marsupials (Didel- 

 phys, Phascogale, Chceropus, Perameles) construct artificial ones. 

 Perameles myosurus, e.g. 6 makes a compact nest in a hollow of 

 the ground, of grasses and other materials, which assimilate closely 



1 cclxxxi". p. 148. 2 cci.xxx". p. 394. 



