208 



Marsupialia ■ 



-MAMMALIA- 



-IIarsupialia. 



state, and transferred by the mother into her marsu- 

 pium, there to be nurtured through the final stages of 

 their fcetal condition, in a manner to be immediately 

 described. Intimately associated with this external 

 specialization of integument, we find the bones of the 

 pelvis, supplemented by two styhform elements, or 

 marsupial trochlear bones, as they are more properly 

 called. Both in the male and female important muscles 

 are attached to these osseous appendages, which are 

 firmly articulated to the anterior border of the pelvis by 

 a broad connecting suriiice, bound down liy interarticu- 

 lar fibrous bands, like those observable in other pelvic 

 synchondroses or ligamentous joints. The marsupial 

 bones vary considerably in diflerent species, bemg 

 elongated, flattened, and curved in the wombat, and 

 comparatively straight and narrow in Perameles. In 

 the koala they are very large and scimitar-shaped, a 

 (fig. 84) ; but only one inch and a half in length in 

 Myrmecobius. The orduaary abdominal muscles con- 



Pelvis and marsupial bones of Ivoala (Pha'^colarctos cinprons)- 



nected with these bones aid them in supporting the 

 maisupium and its contents, but a special muscle 

 — analagous to the so-called " cremaster" of the male 

 — is developed in the female, whose function it is to 

 expel the milk-seoretion of the mammary glands when 

 the young have become located in the pouch and duly 

 attached to the teats. The mode of their connection 

 with the long nipples is very curious ; as, in order to 

 allow of respiratory action being carried on by the 

 foetus in marsupio, it is clearly necessary that the milk 

 should be conveyed directly into the stomach, without 

 the chance of its blocking up the air passages ; and as 

 yet — to take an example — the little kangaroo can 

 hardly display any involuntary functions, such as 

 might regulate the flow of milk, and thereby, in con- 

 nection with the ordinary reflex action of the larynx, 

 obviate the necessity of any special modification of tlie 

 phar^-ngeal organs. To prevent choking, therefore, the 

 windpipe is extended upwards to the soft palatal mem- 



brane, which, acting like a sphincter, embraces its 

 patent outlet, bringing it into immediate contact, and 

 also in continuation w\\\\ the nasal passages. At the 

 same time the teat of the mother is thnist far back in 

 the mouth, and tlie injected milk flows freely down to 

 the stomach, precisely in the same manner as the food 

 of the porpoise, in the first instance, passes the phai-jiix 

 by two passages into the gullet! One can hardly 

 refrain from comment on so remarkable a modification 

 of structure destined to meet the exigencies of these 

 interesting species ; and as, perhaps, our sentiments on 

 this score may derive additional cogency when expressed 

 in the language of an authority — who has contributed 

 more than any other indi\idual to the unravelling ot 

 the intricacies and significance of the marsupial struc- 

 ture — we have little hesitation in inviting attention to 

 Professor Owen's comment, including additional details 

 respecting this organization, as it occurs in the kan- 

 garoo : — " Thus aided and protected by modifications 

 of structure, botli in the system of the mother and its 

 own, designed with especial reference to each others' 

 peculiar condition, and aflbrding, therefore, the most 

 in-efragahle evichnce of creative foresight, the smaU 

 offsprmg of the kangaroo continues to increase, from 

 sustenance exclusively derived from the mother, for a 

 period of about eight months. Dmung this period the 

 hind legs and tail assume a great part of their adult 

 proportions ; the muzzle elongates ; the external ears 

 and eyelids are completed ; the hah begins to be 

 developed at about the sixth month. At the eighth 

 month the young kangaroo may be seen frcqucntlj' to 

 protrude its head from the mouth of the poucli, and to 

 crop the grass at the same time that the mother is 

 browsing. Having thus acquired additional strength, 

 it quits the pouch, and hops at first with a feeble and 

 vacillating gait, but continues to return to the pouch 

 for occasional shelter and supplies of food tiU it has 

 attained tlie weight of ten pounds. After this it wiU 

 occasionally insert its head for the purpose of sucking, 

 notwithstanding another foetus may have been deposited 

 in the pouch ; for the latter attaches itself to a diflerent 

 nipple from the one which had been previously in use." 

 Havuig advanced thus much concerning the most 

 important features of the order, it only remains for us to 

 notice very briefly some other minor characteristics. 

 Speaking generally, it may be said that the numerous 

 species which are thus linked together into one group, 

 present very striking diflerences in their structure, and 

 consequently also in their habits of living. These are 

 for the most part indicated in tlie union of the skull and 

 in the form of the teeth, of the two clavicles into a 

 single furcular bone, and in the condition of the cranio- 

 dental peculiarities bearing a strict relation to their 

 carnivorous and msectivorous propensities on the one 

 hand, and to the mixed natm-e of their food and purely 

 phytivorous habits on the other. In this respect alone, 

 therefore, three or fom-, more or less, natural groups are 

 presented to us. But it is not alone in the skeleton 

 that such correlative peculiarities exist, as many scarcely 

 less interesting de\dations affect the brain, tlie circula- 

 tory organs, the digestive organs, and its associated 

 chylo-poietic \dscera. Lito these, however, it is not our 

 province to enter ; and it must, therefore, suffice us to 



