124 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



described from Cambarus propinquus by Wright and Linton, and Ward (198) lias found 

 in the same crustacean still another species, Distoma opacnm. a The cysts occupied 

 the space in the cephalothorax above the heart and sexual organs." 



The " tomally" or liver of tbe lobster is free, so far as is known, from parasites 

 of all kinds, yet this is not the case with all the decapod Crustacea. In June, 1885, 

 while dissecting the southern shrimp (Penceus setiferus), I found numerous stages in the 

 development of a cestode worm, Tetrarhynchus (species undetermined), in the liver of 

 this prawn. The youngest were oval, about TT o inch in long diameter; the oldest 

 larvae measured yyinch; they had a round, flattened body, an anterior segment or 

 neck, with four well-developed proboscides, and a "tail" of about equal length, and 

 unsegmented. Two pairs of bright red pigment spots were borne on the upper ante- 

 rior part of the body. 



DISEASES OF THE LOBSTER. 



There are no specific diseases to which lobsters are subject, so far as known, yet 

 they sometimes die off so rapidly as to lead one to suspect that they may have fallen 

 a prey to some contagious disease. 



Mr. N. F. Trefethen, of Portland, Maine, who owns a lobster pound in South 

 Bristol, 35 miles east of Portland, relates the following experience: In May, 1893, 

 he placed 100,000 lobsters in this pound, the area of which is about 3 acres. Very 

 soon they began to die, and in a few days all of them were dead. There were 12 

 to 13 feet of water in this pound at flood tide and not less than feet at low water. 

 The pound was probably very much overstocked, but it is difficult to understand why 

 these lobsters should have all died so suddenly, uuless they were either poisoned or 

 attacked by disease. 



In the summer of 1889 a lobster with a large bunch on the side of the carapace 

 was captured in Vineyard Sound. On the top of this tumoid growth was a crater- 

 like depression covered with a membrane. This was probably a sore resulting from a 

 wound which the animal had received in the back, and which had failed to heal. A 

 similar case is mentioned by Rathbun (155). 



