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continuation of the walls of the groove; and from them, by 
and bye, grow out little buds which, by degrees, assume the 
shape of limbs. Watching the fashioning process stage by 
stage, one is forcibly reminded of the modeller in clay. Every 
part, every organ, is at first, as it were, pinched up rudely, 
and sketched out in the rough; then shaped more accurately ; 
and only, at last, receives the touches which stamp its final 
character. 
Thus, at length, the young puppy assumes such a form as 
is shewn in Fig. 14, C. In this condition it has a dispro- 
Fre. 14.—A. Earliest rudiment of the Dog. B. Rudiment further advanced, 
showing the foundations of the head, tail, and vertebral column. 
C. The very young puppy, with attached ends of the yelk-sac 
and allantois, and invested in the amnion. . 
portionately large head, as dissimilar to that of a dog as the 
bud-like limbs are unlike his legs. 
The remains of the yelk, which have not yet been applied 
to the nutrition and growth of the young animal, are con- 
tained in a sac attached to the rudimentary intestine, and 
termed the yelk sac, or ‘umbilical vesicle” Two membranous 
bags, intended to subserve respectively the protection and 
nutrition of the young creature, have been developed from 
the skin and from the under and hinder surface of the body ; 
