128 BULLETIN OF THE BUREAU OF FISHERIES. 



any, but had never happened to examine the flesh of the butterfish. Even those 

 butterfish with cysts in the flesh which were brought to my attention did not at first 

 suggest anything to me other than that they were cases of exceptional and accidental 

 infection. 



Food of the butterfish. — Turning now to the other phase of the subject, it may be 

 inquired, What is the source of the cysts in the flesh of the butterfish? 



Any persistent and regularly recurring case of parasitism when a cestode is 

 the parasite is usually possible only where the final and intermediate hosts are 

 related to each other as eater and eaten. Furthermore, they must be so closely 

 associated in habitat that the. intermediate host in the natural performance of its 

 feeding activities will become infected. In the absence of opportunities to study 

 the habits of the butterfish in its natural surroundings recourse must be had to an 

 examination of the stomach contents in order to ascertain the nature of the food, 

 since it is with the food that cestode eggs and embryos gain admission to the body 

 of the intermediate host. 



The following notes on the food of the butterfish were published in my report, 

 "Parasites of Fishes of the Woods Hole Kegion" (Bull. U. S. Fish Commission, 1899, 

 vol. xix, p. 453) : 



Stomachs of larger fish usually empty, but a few fragments of fish occasionally seen. In the alimentary 

 tracts of smaller specimens copepods, annelids, and small fish were found. Sept. 1, 1900, 2.5 small fish were 

 examined. The food consisted principally of amphipods. 



In the latter part of August, 1903, a few butterfish were examined on three occa- 

 sions by my assistant, Mr. G. F. Englesby. The stomachs were empty in two of 

 the lots; in the other fragments of fish were found. In July and August, 1904, 

 butterfish were examined on several occasions by my assistant, Mr. M. B. Swift. 

 In most cases the stomachs were reported to be empty. In a few cases I examined 

 the digested material with the aid of a microscope and found the setae and jaws of 

 annelids. Pieces of green algse were found on two occasions. Mr. Yinal X. Edwards 

 examined butterfish on October 7, 9, and 16 and found ctenophores in the stomachs 

 on each of these dates and annelids on the 9th. On May 10 he found shrimp. 

 Mr. Edwards states that the butterfish does not take the hook, but is caught only 

 in traps. 



It is evident, I think, even from the above rather meager food notes, that the 

 butterfish eats any small floating or swimming animals which it encounters in the 

 water. 



It should be remembered also that the chyle in the intestines of those hammer- 

 heads in which Otobothrium crenacolle was found in considerable numbers contained 

 large numbers of ripe segments of this tapeworm, which, moreover, continued active 

 for many hours in sea water. Also the segments contained enormous numbers of 

 eggs. It follows from this condition of things that segments containing eggs with 

 embryos are being continually discharged into the water along with the feces from 

 those sharks which harbor this worm in the intestine. Butterfish encountering 

 these free segments would naturally catch and swallow them, as they would any 

 small swimming worm, crustacean, or the like. This is also indicated by the fact 

 that those butterfish which were found to be infected in most cases carried large 



