i2 4 AGE, GROWTH, AND DEATH 



tinct eye, the protuberance caused by the heart. Nos. 

 1 1 and 1 2 show the embryonic shape at twelve and a 

 half and at thirteen days there has been a great in- 

 crease of size with accompanying modifications of 

 form. The next pair, Nos. 13 and 14, present us em- 

 bryos of fourteen and fifteen days, respectively, and 

 you see that the growth is very marked indeed, and 

 the change of form obvious ; the creature is now pass- 

 ing from the embryonic type into something resem- 

 bling a rabbit. Other pictures could readily be added, 

 but, though two weeks must still elapse before the 

 animal will be ready to enter the world, it is not neces- 

 sary for my present purpose to include this period in 

 our survey. We need only contemplate, it seems to me, 

 the series of drawings in Fig. 44 to realise that the early 

 embryonic growth of the rabbit, like the embryonic 

 growth of the chick, proceeds with a speed which is 

 never paralleled by the growth during later stages. 



Now I had a considerable number of rabbit em- 

 bryos preserved in alcohol, and though it was not very 

 accurate to weigh them as alcoholic specimens, in or- 

 der to determine their true weight, yet I resolved 

 to do so as it was the best means at my disposal at 

 the time. The result of that weighing was very in- 

 teresting to me, becaused it showed that in the period 

 of nine to fifteen days the rabbits had, on an average, 

 added 704 per cent, to their weight daily ; but in the 

 period of from fifteen to twenty days, the addition is 

 very much less than this, only 212 per cent. But 

 these rabbits at ten days have already had a consid- 



