302 
ergoes a high degree of reduction, we should be inclined to think, 
that the tail had been still more reduced in the case of the pre- 
sent almost entirely sedentary larvæ. It is only when studying the 
tg ole 
ME mer eg 
Fig. 21. The apex of the anal karen re hemken and the tracheal gilles are omit- 
ted; the drawing shows the chitinous parts which support the dorsal and ve entral 
brush ; a bunch of bristles is mini in each of the holes. 
manner in which the sipho penetrates the plant tissues that WÉ 
understand the importance of the tail. Later on we will return 
to this point, and it will then be demonstrated, that a change has 
taken place with regard to the function of the organ, and that this 
fact fully explains its high development. 
Sipho 
The most peculiar organ of the larva is the sipho (figs-. 22, 
23, 24), by means of which the larva may immediately be distin- 
