:86 



W. L. TOWER. 



ening it to enable it to resist the strain and pressure it must 

 undergo during 'and after ecdysis, and by solvent secretions to 

 weaken the old cuticula and decrease the resistance offered by 

 it to its removal and to provide from the material to be cast away 

 a part of the lubricating fluid, to facilitate the withdrawal of the 

 body from its old cuticula covering. 



The Exnvial Sutures. It is commonly stated that the rupture 

 of the integument during ecdysis is caused by the pressure of the 



.JOS. 



c. 



o 



FIG. 8. L. decimlineata. Section of the head in the region of the occiput. Last 

 larval instar showing the line of weakness formed in the mid-dorsal line by the in- 

 flexed body wall, os, occipital suture ; /, crura of tentorium ; og, occipital fold. 



haemolymph during the contractions. It is probably true that 

 the pressure of the haemolymph and the violence of the contrac- 



