ON TKMNOOEPHALA. 283 



of attachment, the long slender tentacles stretched to their 

 utmost and waving about the water in search of food. Their 

 food consists of small Crustacea (small Amphipoda in the case 

 of the New Zealand species, small Aselli and Entomostracans 

 in the case of the New South Wales species) and insect larvse. 

 These they capture by means of the tentacles, and it is 

 readily to be understood that living on the crayfish must be of 

 advantage to the animal, the movements of the crayfish in 

 searching for food amongst the stones and dead leaves and 

 sticks on the bottom of the stream doubtless starting many of 

 these Arthropods, and enabling the Trematodes to secure them. 

 The Temnocephalse move from place to place with a sort 

 of " looping " action very like the movements of a leech. The 

 body is applied to the surface of the crayfish and then stretched 

 out ; the tentacles become shortened aiid flattened out on the 

 surface of the crayfish and play the part of anterior suckers • 

 the large sucker is relaxed and the body drawn forwards by 

 means of the tentacles, until the sucker is fixed again close up 

 to the latter, the body being now bent double ; the tentacles 

 then let go their hold, the body is stretched out again and so 

 on. The body can be rotated from side to side through a verv 

 large arc by the action of the sucker, which is capable of a 

 considerable amount of rotation around its short stalk. 

 The rapidity of all these movements and the extreme sensitive- 

 ness of the animals are surprising. A slight touch from an 

 instrument wiil cause an instantaneous turning aside of the 

 body, drawing in of the tentacles, and frequently rapid flight 

 in a different direction from that in which the attack was 

 made. In turning aside from a touch the little animals show 

 a very definite sense of direction, and if a succession of taps 

 be made on the bottom of a vessel in which they are livin°- 

 alternately on opposite sides of them, they will turn from one 

 side to the other according to the direction of the tap. If 

 they are detached from the surface of the crayfish — which it is 

 very difficult to do owing to the slippery character of their 



integument and the firmness with which the sucker adheres 



they contract themselves for a moment into a ball, then stretch- 



