PHRYXUS HYNDMANNI. 245 



head. The legs are very robust, but folded so as not to 

 extend beyond the sides of the body. The tail is com- 

 posed of six joints, gradually diminishing in width, the 

 last being very small, nearly oval, the tip pointed, and 

 with a minute seta on each side beyond the middle. 



Dr. Fritz Miiller, in a letter to us dated in 1864, 

 observes, that " One of the most interesting animals of 

 this family is a Bopyrus living on Pagurus, in which the 

 dorsal surface of the parasite is directed towards the 

 Pagurus (I therefore named it B. resupinatus) . The origin 

 of this curious manner of attachment is the following : 

 The larva of Bopyrus fixes itself to the Sacculina purpurea, 

 living on the same Pagurus, and takes its nourishment 

 from the roots of the parasite. After the death of 

 the Sacculina, to whose ventral surface the Bopyrus was 

 fixed, the latter probably cannot change its position, and 

 remains with its dorsal surface facing the Pagurus." 



