So Records oj the Indian Museum. [Vol. IX, 



person knows, or may easily know, how the disease is communicated and what 

 part is played in the matter by the pig and by rats and mice. 



" The immense value to humanity of such a discovery as the cause of malaria 

 and of yellow fever is entirely beyond our powers to estimate ; and yet, this 

 value must not be credited to this one discovery alone, as if it were a thing apart. 

 No less credit must be given to the long line of investigators whose persistent 

 interrogations of nature have led up to this discovery, and will surely lead to 

 others no less valuable." 



Linton's remarks apply very aptly to the situation of affairs in 

 India. As our knowledge of the parasites of freshwater fish in India 

 is at present nil, it is impossible to say to what extent the inland 

 fisheries in particular are affected through this cause. As far as 

 we know, there are no fish parasites in India capable of infecting 

 man. In Europe, the larva of Bothriocephalus latus (a worm 

 inhabiting man and often measuring 20 to 30 ft. in length) occurs 

 in the Pike and is transmitted from this host to man ; but up 

 to the present this worm has not been recorded from India. It 

 is just possible that a certain rare Trematode {Gasterodiscus 

 hominis, Lewis and McConnel) recorded twice from man in 

 Calcutta, ma}^ have its earlier stages either in the flesh or on the 

 skin of certain fish. As far as we know at present, the bad 

 effects of parasitism amongst fish are confined, in Bengal, entirel}^ 

 to the fish themselves, and amongst those forms inhabiting fresh- 

 water tanks these effects tend to be cumulative. An illustra- 

 tion will emphasize my meaning. 



In the following paper is recorded a large larval worm {Ligula 

 simplicissima) from the coelom of Laheo calbasu. This worm 

 has its adult stages in a certain bird. Such birds live in the 

 vicinit}^ of the tanks containing the fish on which they feed. 

 When a bird becomes infected, the parasite matures in the bird's 

 intestine and passes millions of eggs to the exterior with the bird's 

 faeces. Such faeces are often dropped in a tank and provide an 

 extensive source of infection to the fish in the tank. The cumula- 

 tive infection of the fish is due solely to the fact that such 

 tanks have no current of running water. To what extent such 

 infection exists in Indian fish has still to be determined. Infected 

 fish are almo.st always thin, emaciated, undersized and lacking 

 in vitality. 



Of the Cestode parasites, the majority occur in the gut or on 

 the mesenteries, and are thus removed before the fish is eaten. 

 Up to the present no Cestode parasite, or cyst, has been recorded 

 from the flesh of any fish in India. The Trematode parasites 

 may occur either on the skin or in the gut, or, as in the case of 

 the Mahseer recorded in this paper, the parasite may infect the 

 muscles. 



Of other causes resulting in the disease of fishes, such as 

 parasitic Crustacea, Acanthocephala, Nematodes, infectious para- 

 sitic fungi, infectious parasitic Protozoa (Myxosporidia) and bac- 

 teria, India provides a new field of work, and at present it is 

 impossible to say to what extent the inland fisheries suffer through 

 the effects of such parasites. 



