I2o6 BULLETIN OF THE BUREAU OF FISHERIES. 



can not fail to be attractive to small fish. These small fish, especially when 

 traveling in schools, must themselves often pay tribute to the shark. There is 

 thus established by the common bond of mutual advantage an association 

 which must be extremely favorable to the parasite which can thrive well in both 

 the intermediate and the final host which are the principals in this association. 

 From time to time the ripe joints of the cestode will be discharged into the water 

 along with the fseces from the intestine of the shark. These joints look, behave, 

 and doubtless feel to a small fish much as other small swimming forms, ento- 

 mostracans, annelids, and the like do, and consequently are picked up by them. 

 In some such manner do the eggs of the cestode gain lodgment in the intermediate 

 host. What is difficult to picture is the actual situation which not only makes 

 possible but actually brings to pass the infection of practically all the butterfish. 

 A study of the appended tables will make it quite clear that among the half 

 grown and fully grown butterfish an individual which is free from these cysts 

 in the flesh is exceptional. 



Butterfish are not fish of rare occurrence traveling singly or even in very 

 small schools. They are taken in considerable numbers in the fish pounds, and 

 evidently move in fairly large schools. How far they migrate along the coast 

 is not known. I have found the adult cestode, though not abundant, in the 

 sharp-nosed shark at Beaufort. This shark is abundant. The other known 

 final host is the hammerhead shark, which is not an abundant species, though 

 it is one which has a wide distribution. I hope to be able to gather more data 

 on this interesting problem of distribution. 



GENERAL CONSIDERATIONS AS TO FLESH PARASITES OF FISHES. 



To what extent is the food value of fishes impaired by the presence of para- 

 sites in the flesh? 



With the exception of the common butterfish {Poronotus triacanthus) , and 

 its rarer relative the har^^estfish {Pepribis alepidotus), I find that the marine 

 food fish I have thus far examined are so free from parasites in the flesh that the 

 question has, at present, little more than an academic or rather a purely zoolog- 

 ical interest. To take the case of the butterfish, it may be remarked: 



I . Since the cvsts might be easily mistaken for ova by one whose knowledge 

 of the natiu-al position of the ovary is indefinite, and since the nutritive value of 

 the cysts is doubtless little different from that of so much fish-roe, it is likely 

 that the food value of the parasitized fish is not much different from that of the 

 nonparasitized or but slightly parasitized fish of the same weight. There is no 

 evidence of any inflammatory or pathological condition of the tissues of the fish 

 brought about by the presence of the cysts. From another point of view the 

 cysts are a decided detriment. A number of badly parasitized fish was selected 



