284 WILLIAM A. HASWBLL. 



ing themselves out to their full length and extending their 

 tentacles, they are often able by strong flexions of the body 

 while falling through the water to seize on some other part of 

 the surface and regain their position on the crayfish. The 

 movements thus made in the attempt to regain a hold are not 

 unlike the movements made by the leech when swimming, but 

 the Temnocephalse are incapable of directed movement or 

 even of sustaining themselves in the water by this means. 

 When the body is pinched or cut, the tentacles are very often 

 turned backwards and clasp the instrument used as if to ascer- 

 tain its nature or to repel the attack, and the tentacles are to 

 be regarded as special organs of touch as well as instruments 

 of prehension and aids to locomotion. 



Four very distinct species of Temnocephala frequent the 

 Australian and New Zealand crayfishes, and all of them, so 

 far as I am able to judge from Philippics figures, differ from 

 T. chile nsis. That found on the surface of the larger 

 Tasmanian crayfish, is distinguished by the possession of a 

 short compressed lobe instead of the median tentacle. All 

 the others have, like T. chilensis, five equal or nearly equal 

 tentacles ; but are to be distinguished from one another by 

 certain differences in the structure of the reproductive organs 

 to be noticed later on. 1 propose the following names for the 

 four species : 



1. Temnocephala fasciata, on Astacopsis serratus, 

 streams of New South Wales. 



2. T. quadricornis, on Astacopsis Frank linii, northern 

 rivers of Tasmania. 



3. T. minor, on Astacopsis bicarinatus, streams of 

 New South Wales. 



4. T. NoViE-ZELANDi^E, on P ar a ne p h ro p s setosus, rivers 

 of New Zealand. 



Integument, Muscles, and Parenchyma. 



The body wall is composed of the following layers — cuticle, 

 epidermis, basement membrane, circularly arranged layers 



