INCREASE IN SIZE OF EGGS. 



121 



of the eggs of some increasing in size during the pro- 

 cess of hatching. The fact appears to have first been 

 noticed by the celebrated Vallisnieri in his observa- 

 tions on saw-flies (Tenihredinidcz, LEACH).* Other 

 instances were subsequently discovered by R aumur, 

 De Geer, Derham, R' sel, and the younger Huber. 

 ' It ought not,' says R aumur, speaking of gall flies 

 ( Cympidce, WEST WOOD), ' to be passed in silence, 

 that the egg which I found in the gall appeared to 

 me considerably larger than the eggs of the same spe- 

 cies when they proceed from the body of the fly, or 

 even when they are taken from the mother fly near the 

 time of their being laid. The whole of those I took 

 front the mother flies which I killed were remarkably 



Generation of a water-mite (Hydra-hna alstergens). 

 a a, the water scojpion, in whose body the mite fixes her eggs. 

 6 b, a magnified view of one of its claws, c, a tooth-like process for 

 restraining the motion of the joint. <Z, the water-mite, e, a greatly 

 magnified view of one of its eggs, y, the hook by which it is inserted 

 into the body of the scorpion. 



* See Insect Architecture, pp. 157-8. 

 VOL. VI. 11 



