SEA-FISHERIES LABORATORY. 279 



of pearly lustre. The general appearance of one of these 

 cysts is represented in PL V., fig. 15, as seen under a low 

 magnification. The trematode lies inside two cysts, of 

 which the outer is rather thick and fibrous, and is pro- 

 bably derived from the tissues of the host. The inner 

 cyst is very thin and delicate, and is quite transparent. 

 This investment is probably parasitic in origin, and 

 inside it lies the parasite with the anterior extremity bent 

 sharply round the swollen bulbous posterior extremity. 

 Fig. 9 is a view of the trematode within the inner cyst 

 wall, and lying with head bent away from the observer. 

 Fig. 10 again shows one of the worms dissected out from 

 the sac and partially straightened out. The longest 

 diameter of one of the largest cysts is about 2 mm., but 

 most of them are much smaller. The length of the 

 trematode, bent up as in fig. 9, is 0*72mm., and its extreme 

 length, if straightened out, would be about 1*25 mm. 



The hinder portion of the body is swollen out into a 

 kind of bulb, and is nearly filled up with a uniform kind 

 of tissue, granular and rather like the yolk material in 

 some eggs. The intestinal branches run back over this 

 for some distance, and end blindly. The anterior portion 

 of the body is cylindrical, and a short neck or constricted 

 portion separates it from the head. This latter portion is 

 very characteristic, because of the double series of spines 

 which surround the terminal mouth. This double 

 arrangement of the oral spines can be seen in every 

 specimen, though at times it is not very distinct. Fig. 14 

 represents the head seen from the side. The spines are 

 very much stronger than those on the body. Except for 

 these two circumoral rows, the greater portion of the 

 head in this specimen was devoid of spines, though in 

 some others small spines seemed to be present here also. 

 The body as far back as the bulbous portion is closely 



