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KNOWLEDGE & SCIENTIFIC NEWS. 



[May, 1905. 



To make the parental back serve the purptose of a 

 perambulator seems, indeed, to be fashionable among 

 South American animals, for Mr. Hudson tells us that 

 the females of the large aquatic rodent of that country 

 locally known as the coypu or nutria (Myopolamiis 

 coypu) are in the habit of carrying at least some por- 

 tion of their family \\hile swimming. Not that the 

 little coypus, which usually number eight or nine, 

 cannot swim perfectly well by themselves, but 

 they are probably unable to keep up the pace for any 

 distance, and it is quite common to see as many as can 

 find room comfortably seated on their mother's back, 

 and the rest swimming behind on the look-out for their 

 turn for a ride. Whether beavers and water-voles ever 

 carry their offspring about in this manner I have been 

 unable to ascertain. 



It is stated, however, on good authority, that the 

 young hippopotamus is often carried on the back of its 

 mother as she swims, although it is somewhat difficult 

 to imagine how the little creature can maintain a 

 secure foothold on such a slippery surface. Be this as 

 it may, it is evident that the hippo, even though larger 



HiK. 2. — Female Opossum 



-.jd Vojnif. From Elliot's "Mail 

 Middle America.") 



than a good-sized boy, cannot be much of a burden to 

 its colossal parent. A creature which habitually 

 carries about its offspring on its back is the female 

 koala (Phascolarctiis koala), the native bear of the 

 Australian colonists, which dwells among the highest 

 branches of the lofty blue gum-trees, where it may be 

 descried on moonlight nights by a practised observer 

 when thus loaded (Fig. 3). The thick woolly coat of the 

 parent affords excellent foothold to the young koala ; 

 and since there appears to be never more than one of 

 the latter, the burden to the female cannot be excessive. 

 The koala is a member of the marsupial order, in all 

 the species of which the young are born in a helpless 

 condition, and cling for some time to the nipples of 

 the parent. After this they are usually carried for a 

 period in the pouch in which the nipples are situated. 

 The sojourn of the young koala in the pouch after 

 leaving the nipple, if it takes place at all, must, how- 

 ever, be very short, as the creature takes a seat on the 

 maternal back while still small. 



The American opossums are likewise members of the 

 marsupial order, but they present some very remark- 

 able variations in regard to the development of the 

 pouch. The common or typical species, for example, 

 takes its name of Didelphyi marsupialis from the pre- 

 sence in the female of a large and capacious pouch, in 

 which the numerous members of the family are carried 

 about until they attain a very considerable size and 

 become a serious hindrance to the parent in getting 

 about. On the other hand, in the above-mentioned 

 South American species, commonly known as the 

 thick-tailed opossum (D. crass icaitdata), and likewise 

 in the much smaller D. darsigtra, the pouch is rudi- 

 mentary and functionless, and the young arc carried 



about on the back of the female parent in the manner 

 alreadv described. Considering that all three species 

 are thoroughly arboreal in their habits, the reason for 

 the loss of the pouch in the two latter seems altogether 

 inexplicable. If the female of one species can climb 

 with her pouch full of young, there is no apparent 

 reason whv those of all the species should not be al)le 

 to do the same; and so far as the young are concerned, 

 they would seem, at all events in the younger stages 

 of their existence, much better off in a nice warm 

 pouch than in a somewhat precarious and decidedly 

 exposed position on their parent's back, where, how- 

 ever, they have much better opportunities of seeing 

 somethintr of the world. 



Fijf. 3. — Female Koala carrying its Cub. 



The females of all the species of kangaroos, 

 wallabies, and rat-kangaroos always carry their off- 

 spring in the pouch until they are of very considerable 

 size and quite able to look after themselves. In most 

 cases there is only a single young one, but a second 

 may be born before the first has quitted the pouch. 

 In the case of the larger kangaroos, the young, or 

 ■• Joey," which may be the size of a hare before it 

 finally leaves the pouch, must be a very serious burden 

 to the female when at speed. This is proved by the 

 fact that although when first pursued the female parent 

 will pick up and deposit in the pouch the " Joey " 

 running by her side, yet that when very hard pressed 

 she will not hesitate to eject her offspring and leave it 

 to its fate in the hope of saving her own life. 



The cuscuses of the Austro-Malayan islands and the 

 phalangers — the mis-called opossums — of Australia it- 

 self, which are thoroughly arboreal creatures, all carry 

 their young in pouches. Although there may occa- 

 sionally be twins, as a rule there is but one at a birth, 

 .so that the mother is not burdened to any excessive 

 extent by her load. Of the breeding habits of the 

 flying-phalangers, or flying-opossums, of Australia, 

 little or nothing seems to have been recorded; but 

 since they have pouches, it may be assumed that 

 the young, which arc frequently four in number, are 

 carried about by the female. As to the pigmy flying- 

 phalangers— the flying-mice of the colonists — it is diffi- 



