150 



ZOOLOGY 



occurs between two segments which are free in the first larval 

 stage. This power of protective mutilation occurs in those 

 appendages which are most apt to be seized, — namely, the 

 five thoracic legs, — and is wholly under the control of the 

 reflex nervous system, for it may occur when the entire volun- 

 tary nervous system has been removed. The leg of a dead 



Fig. 151. — Larval view of lobster, extracted from an egg 

 which was about ready to hateli. Tlie concretions in the 

 intestine are destined to go into the new cuticula after 

 molting. X 25. From Herrick. 



crustacean shows no such capacity. If the leg of a lobster is 

 cut off at some point beyond that of normal rupture, the limb 

 will later he found cast off up to this point. Here a sort of 

 double membrane or diaphragm exists, with a central opening 

 only large enough to admit the passage of nerves and blood- 

 vessels. ^Upon rupture this passage is soon i^lugged up by 

 coagulated blood — clearly a device to prevent excessive 

 hemorrhages. Soon after a leg is cut off a papilla-like body 



