DEVELOPMENT OF PHEYGANIDS. 551 



It is extremely penetrating and lasting, and cannot be 

 distinguished from that of ordinary musk ; it is quickly ab- 

 sorbed by water and retained for several weeks even after 

 the gelatine has been removed. 



To my knowledge this is the first instance that has been 

 recorded where any peculiar odour has been detected in eggs or 

 their envelopes. It may possibly serve as an antiseptic to 

 prevent the too speedy putrefaction of the gelatine, or perhaps 

 to attract parasites and infusoria, which latter furnish food for 

 the young larvae. 



There is no reasonable doubt as to the identity of the species 

 that laid the eggs. Both males and females of this insect, 

 which Dr. Ha\gen, of Cambridge, Mass., has kindly identified 

 for me as Neophalax concinnus, were observed in great 

 numbers just before twilight flying about over the surface of 

 the water ; although watched very carefully they were not 

 observed to oviposit. The eggs are probably laid after dark. 

 Gravid females were found containing eggs and a gelatinous 

 secretion identical in odour and appearance to those found in 

 the water. 



Eggs in difierent stages of development vary considerably 

 in size and shape. They are spherical during the formation of 

 the embryonic membrane as well as after the revolution of the 

 embryo ; in all other stages previous to revolution they are 

 oval. 



As development proceeds the eggs increase in size to a very 

 marked degree, and by the time they are ready to be hatched 

 the diameter has increased by one fourth or one fifth of its 

 original size. Rathke was the first to call attention to this 

 peculiarity ; he observed it in the case of Gryllotalpa as 

 well as in Phryganids. I have not only been able to confirm 

 his statements in regard to Phryganids, but also to extend them 

 to one of the Locustina, i. e. fficanthus, and to Blatta. In 

 both the latter cases the increase in size could not be due to 

 the appropriation of material from gelatinous envelopes since 

 there are none. In all cases the increase in size of developing 

 eggs is probably due to the conversion of a large amount of 



