484 



ON INCREASE IN SIZE 



[PT. Ill 



1898 that the embryo oi Sphenodon, the tuatara Hzard, had an incuba- 

 tion period of 13 months, of which something hke 9 were spent in 

 a hibernatory state. Boulenger observed much the same thing in 

 the case of the European pond-tortoise, Emys orbicularis, which has 

 an apparent incubation period of no less than 23 months. Still more 

 extraordinary is the case of some mammals which possess the power, 

 according to Reinhardt and Prell, of hibernating in the embryonic, 

 partly-completed, state (mole, roedeer, bear, badger, pinemarten, 

 and stonemarten) . And as for the insects, Regen has shown that the 

 eggs of a locust, Thamnotrizon apterus, laid in September, hibernate two 

 or three winters and finally hatch out in March. Hibernation, indeed, 

 is very common among insect embryos, the mosquito for instance 

 {Aedes flavescens) occupies 7 months in its ^gg (Hearle). 



Table 63. Gestation times of mammals. 



