MUSEUM OF COMPARATIVE ZOOLOGY. 3 



secured by Mr. Agassiz so evidently depended on finding a suitable 

 food for them, that I spared no pains to accomplish this end. Many 

 kinds of meat and fish were minced and fed to them, but none of these 

 was acceptable. The minced liver, which Mr. Agassiz used with success 

 at first, was likewise refused. Fragments of meat were suspended in the 

 water by fine threads, but neither when moved about nor when left per- 

 fectly quiet did they seem to attract attention. Great numbers of water- 

 fleas (Cladocera) were put in the water with the young fishes, but the 

 latter made no attempts to catch them. It was not until after many 

 fruitless trials that organisms were found which were seized with such 

 eagerness, and so persistently, as to leave no doubt that they were the 

 natural food of the young gar-pike. These were the larvce of the common 

 mosquito. They constituted the exclusive diet of the young fishes until 

 the latter became large enough to catch and swallow minute "mud 

 minnows " (Fundulus), on which they subsequently fed as long as they 

 were kept alive. 



When it was once ascertained that the young fishes would take mos- 

 quito larvae, there was no longer any serious question about the feasibil- 

 ity of rearing them, nor was it doubtful that these larvae formed their 

 natural food, for the shallow and quiet waters at the margins of Black 

 Lake and along the creeks which feed it abound in mosquitos. It 

 was by means of this diet that the fishes were kept in a thriving con- 

 dition during the stages immediately following the absorption of the 

 yolk. 



From the 20th of June until the 1st of July specimens were, with a 

 few exceptions, killed every twenty-four hours; and from the 1st of July 

 until the beginning of August, usually at intervals of about forty-eight 

 hours. 



By the 3d of August there remained besides those which had not 

 been preserved only about a dozen living fishes. On that date I started 

 for Newport, E. I., travelling by rail to New York. These remaining 

 fishes were carried by hand in a tin pail suspended by a spring ; but 

 owing to the difficulty of carrying in the pail a sufficient number of 

 mosquito larvae, and more particularly to the impossibility of properly 

 renewing the water, about half of them succumbed to the unfavorable 

 conditions of railway travel and were put into alcohol. One more died 

 on the way from New York to Newport ; but the remaining ones, hav- 

 ing been fed on larvae after my arrival at Newport, appeared to thrive. 

 At the end of a month they were taken to Cambridge, where they were 

 put into a large glass jar and supplied with running hydrant water. 



