114 



NEMERT1NEA 



[CH. 



protruding from the front end of the body at the same time. It can 

 never be completely turned inside out, for certain cords traversing 

 the proboscis-sheath restrain it. At the point in its wall which is 

 at the anterior end when the process of turning inside out has 



reached its utmost limits, 

 there is in the higher Nem- 

 ertines a short lateral pouch 

 in which a horny spike, the 

 stylet, is secreted. Round 

 the base of this open poison- 

 glands, so it can be seen that 

 the proboscis is an offensive 

 organ for seizing prey. So 

 far as we know all Nemertines 

 are carnivorous. Amongst the 

 lower Nemertines the stylet 

 is not developed, nevertheless 

 the proboscis can be employed 

 to catch prey; it is quickly 

 thrust out and coiled spirally 

 round the victim and then 

 retracted so as to push the 

 prey into the mouth. This 

 retraction is brought about 

 by a muscular band which 

 attaches the end of the pro- 

 boscis to the sheath. The land 

 Nemertines (Geonemertes) are 

 said to travel by thrusting 

 out the proboscis, attaching 

 it to foreign objects and 

 drawing up the body after it. 

 Fw. 48. Linens geni.cnlatusx%. Underneath the ciliated 



1. Lateral slits on head. 2. Anus. ectoderm O f Ne mertines there 

 is a series of powerful circular and longitudinal muscles : these 

 layers are continued, but in the reverse order, on to the walls of 

 the proboscis, since this is only invaginated skin. Under extreme 

 irritation the extended proboscis is sometimes torn from the 

 body by the heightened pressure of the fluid in the sheath 

 and in one instance such a disjoined proboscis was mistaken on 

 account of its active contractions for a new species of Nemertine. 



