652 WILLIAM PATTEN. 



highly concentrated and compact food yolk, containing fats and 

 oils, into a less dense and more irregularly distributed proto- 

 plasm by the absorption of water, oxygen, and nitrogen from 

 the surrounding media. Oxydation is necessary for all vital 

 activity, and nitrogen is necessary for the conversion of fatty 

 substances into protoplasm. A certain amount of moisture is 

 necessary for the development of eggs which are not normally 

 deposited in water, for such eggs will not develop in a dry 

 atmosphere. 



The eggs when first deposited are distinguished by the 

 whitish colour and hard, compact appearance of the gelatinous 

 matrix, which slowly swells and becomes very transparent 

 through the action of the water and decay. 



Zaddach states that the larvse feed upon the softened gelatine 

 and the numerous Infusoria which it contains at the time of 

 hatching. As far as the gelatine itself is concerned he is prob- 

 ably in error, since the larvae on rupturing the chorion leave 

 the jelly as quickly as possible. Moreover, a great many of 

 these empty gelatinous masses were found which did not indi- 

 cate that the larvse had fed upon them. I do not doubt, how- 

 ever, that the larvse find a welcome store of food in the various 

 Infusoria which infest the gelatinous matrix at the time of 

 hatching. 



The question at once arises to what use can these envelopes 

 be applied. To be sure they hold the eggs together in one mass, 

 but as regards protection from their enemies there is more 

 danger in this way than if they were scattered irregularly 

 about. The eggs are undoubtedly eaten by other animals, and 

 when collected into aggregates all sufi'er the same fate, which 

 would not be the case if they were isolated. 



In all Phryganids, with the exception of the present species, 

 the gelatine serves to fasten the eggs to various objects of 

 more or less stability. The eggs of Neophalax, as well as some 

 species of Chironom-us, are suspended in a jelly which floats or 

 lies freely in the water. In other species of Chironomus, 

 according to my own observations, the eggs are fastened to 

 some stick or stone. 



