232 The Alligator and Its Allies 



before he succeeded in obtaining all the desired 

 stages of development. 



To obtain the earliest stages, I watched the 

 newly made nests until the eggs were laid, and in 

 this way a number of eggs were obtained within a 

 very few hours after they had been deposited, and 

 all of these eggs contained embryos of a more or 

 less advanced stage of development. Gravid 

 females were then killed, and the eggs removed 

 from the oviducts. These eggs, although removed 

 from a "cold-blooded" animal, generally contained 

 embryos of some size, and only one lot of eggs thus 

 obtained contained undeveloped embryos, which 

 embryos refused to develop further in spite of the 

 most careful treatment. Voeltzkow (78) found, 

 in the same way, that the earlier stages of the 

 crocodile were extremely difficult to handle; so 

 that, in order to obtain the earlier stages, he was 

 reduced to the rather cruel expedient of tying 

 a gravid female and periodically removing the eggs 

 from the oviducts through a slit cut in the body 

 wall. 



The older embryos are hardy and bear trans- 

 portation well, so that it is comparatively easy 

 to obtain the later stages of development. 



For the stages up to the formation of the first 

 four or five somites, I am indebted, as I have 

 already said, to Professor Clarke, and, since I 

 have had opportunity to examine only the sections 

 and not the surface views of these stages, I shall 



