12 MARSUPIAL “ LARVAE ” CHAP. 
are the precise equivalents of similar bones in the Monotremata. 
It has been held, but apparently erroneously, that these bones 
are mere ossifications in the tendons of the external oblique 
muscle of the abdomen, or of the pyramidalis of the same region ; 
and vestiges have been asserted to exist in the Dog. Such 
bonelets are undoubtedly present in the 
Dog; but it seems clear from their develop- 
ment in Marsupials, as structures actually 
continuous with the median unossified por- 
tion of the symphysis pubis, that the 
“marsupial bones” belong to that part of 
the skeleton, and that they correspond with 
the epipubis of certain amphibians and 
reptiles. The pouch, it may be remarked; 
exists in a rudimentary form in the males 
of many Marsupials. 
The most salient feature in the life- 
history of the Marsupials is the imperfect 
condition in which the young are born. 
The egg is no longer 
laid, as in the Mono- 
tremes; but curiously 
enough the ovum, 
which has the small 
size of that of the 
Eutheria, divides in- 
completely at the 
first division (as Mr. 
Fic. 60.—Ventral surface of 
innominate bone of Kan- 
garoo (Macropus inajor). 
x 4. a, Acetabulum ; ab, 
acetabular border of ilium ; 
is, iliac surface ; mm, ‘‘ mar- 
supial” bone; pb, pubic 
border ; pt, pectineal tu- 
bercle ; s, symphysis ; si, 
supra -iliac border ; ss, Caldwell has shown), 
sacral surface ; thf, thy- oe : 
roid foramen; #7, tuber- and this develop- 
osity of ischium. (From mental feature may Fic. 61.—Mammary foetus 
Flower’s Osteoloqy.) of Kangaroo attached to 
perhaps be looked the teat. (Nat. size) 
upon as a reminiscence of a former large- 
(From Parker and Has- 
ae well’s Zoology.) 
yolked condition. The young when born 
are small and nude; the newly born young of a large Kangaroo 
is perhaps as large as the little finger. The young are trans- 
ferred by the lps of the mother to the pouch, where they are 
placed upon a teat. It is an interesting fact that they are 
not merely imperfect foetuses, but that they are actual larvae. 
They possess in fact at any rate one larval organ in the shape of 
