On Stichocotyle nephropis Cunninf^ham, a parasite of the American lobster. 451 



used either sinjîly or in groups; often, on trying to take up the worm 

 by a pipette, when it was lying in a comparatively quiet condition, it 

 was found to be attached by a considerable number of suckers — half 

 or more of the total number present. The hold of the animal on a 

 smooth glass surface was so strong that it was difficult to remove it 

 except by a sudden movement when it was unprepared to resist. 



How long these young worms could be kept alive in sea-water was 

 not determined, since the number of worms which I had was too 

 small to warrant that kind of experimentation. Those which had been 

 kept for 24 hours free in see-water still appeared active and healthy. 



Stichocotyle, in the stage of developement at which it is found 

 encysted in the lobster, is, in a normal state of contraction, from 

 3 — 7 mm long and */, — ^/^ mm thick in the largest part of the body. 

 It is of a whitish color and of a generally cylindrical form , but 

 tapering a little toward either extremity (PI. 29, Fig. 2). The greatest 

 thickness is in a region about one fourth of the animals length from 

 the head end. From here backward the body gradually diminishes 

 in size. A transverse section of the body in any region is nearly 

 circular and varies from this condition only when the section passes 

 through a sucker. The mouth is ventral and near the anterior end 

 and its lips are able to perform the function of a rudimentary sucker. 



Along the mid-ventral line of the body is a series of suckers 

 arranged in a single row. They begin a short distance behind the 

 mouth and extend backward very nearly to the posterior end of the 

 body, gradually becoming smaller toward the latter end of the series. 

 The number is, in the immature state at least, not definite. Cun- 

 ningham found it to vary from seven in the smallest worms to twenty- 

 two in the largest. 



These limits exceed somewhat those which I have found, but 

 this is not ])e wondered at, as he had so many more individuals for 

 examination. According to my observations, however, the larger worms 

 usually have fifteen or sixteen suckers, as stated by him. 



In the cyst the worm lies rolled up into a coil of about one and 

 one half turns. I have never found a cyst to contain more than one 

 worm, though Cunningham states that several worms may be found 

 in the same cyst, as many as five having on one occasion been taken 

 from a single cyst 



The excrctor}' pore is upon the dorsal surface near the posterior end. 



The sexual pore is median, ventral, and a little in front of the 

 anterior edge of the first sucker. 



