324 BULLETIN OF THE BUREAU OF FISHERIES. 



sparrow. It should not require much reflection to convince anyone that before an 

 adequate answer can he made to such an inquiry trustworthy observations must be 

 made by competent investigators on the feeding habits of this bird, both adult and 

 young, in different localities throughout the year and through a series of years. 

 But the general public may wish to know, and in this ease has a right to know, what 

 advantage (here is to it in such scientific inquiry as is implied by an investigation 

 made on the food and the parasites of fishes. 



It may. 1 think, be confessed that, so far as may he seen while the investigations 

 are in progress, much of the information which is collected will lie of interest only 

 to zoologists. In view, however, of the well-known fact that many diseased condi- 

 tions and even epidemics result from the presence of parasites, and. further, that the 

 parasites are as a rule introduced, either as eggs or larva', along with the food, it is 

 not difficult to see that the more complete and systematic our knowledge becomes of 

 (he interrelations of the animals which harbor the parasite— interrelations which 

 depend very intimately on the food habits of fishes — the more certain are we to be 

 able to cope successfully with any disease which may arise. A case in point is fur- 

 nished by one of the recent triumphs of medical knowledge. It is scarcely possible 

 that the cause of malaria and of yellow fever could have been discovered if it had not 

 been for the previous contributions to knowledge made by investigators in parasitism. 

 The germ of malaria is a parasite whose round of lite is passed in the blood cells of 

 man and in certain organs of the mosquito. The germ of yellow fever seems to have 

 a similar history. These interrelations between the mosquito and man were not even 

 dreamed of a generation ago. The history of trichinosis is now so well known that 

 a simple allusion to it in this connection is sufficient. Every well-informed 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. 



In the summer of 1901 the material for study upon which this paper is based 

 was obtained in large part from the fish market, and therefore came from fish of 

 adult size. The following year a good deal of seining was done by the laboratory 

 party. Almost every day, in fact, during the latter half of the season, the seine was 

 dragged in the harbor and adjacent waters. This placed at my disposal not only 

 several species of fishes which had not been examined the preceding year, but. as a 

 rule, much smaller individuals of the common food fishes of the region than those 

 which are taken to the markets. The number of fish examined in 1901 was N4'2; in 

 l!M>-_! the number was 1,209. As a rule only the viscera and body cavity were 

 examined for entozoa, although occasionally search was made in the muscles for 

 parasites encysted in the flesh, and the character of the food was always noted. 



The authority for the names of fishes in this report is Jordan and Evermann's 

 Fishes of North and .Middle America. 



The faithful and efficient work of Mr. C. W. Stone, who assisted me in the 

 collection of material, is most gratefully acknowledged. 



