398 



EMERGENCE OF DRAGONFLY-LARViE, 



Table showing hatchings of Eggs of Anax jKipuensis, 

 March 2 8th- April 11th, 1916. 



L denotes that the emerging embryo reached the full larval 

 stage, P that it did not succeed in getting beyond the pronyniphal 

 stage. None of the larvte obtained from Series A lived more 

 than two or three hours. The pronymph marked * was from the 

 unreversed embiyo, and came out of the egg-shell backwards. 



Section 2. — The Composition of the Gas in the Tracheal System. 

 The question next arose — What could be the composition of 

 the gas which I had seen enter the tracheal system from the 

 body of the pronymph? It seemed to me, as soon as I observed 

 the phenomenon, that it must be one of two things, viz., {a) car- 

 bonic acid gas, or (6) oxygen. The former would naturally 

 appear to be the most likely solution, since C0„ is the only gas 

 formed in large quantities within the body of a living animal. 

 On the other hand, one naturally recoiled at the idea that such a 



