704 



ZOOLOGICAL SOCIETY BULLETIN. 



seventeen and one-half pounds. Two have died 

 during the past summer, but tlie others seem to 

 be in good condition. 



A census of tlie inliabitants of the Aquarium. 

 made a short time since, showed the following 

 numbers : 



Species Specimens 



Fishes lOS 234-1. 



Amphibians 11 107 



Reptiles 19 160 



Mammals 2 1 



Invertebrates 24 815 



Total 164 3430 



R. C. O. 



CICHLID FISH AT THE AQUARIUM. 



IN the fresh water rivers and lakes of Central 

 and South America the members of the family 

 Cichlidae take the place of our sunfishes and 

 basses. The species, which are very numerous, 

 are mostly referable to the closely related 

 genera CicMosoma and Heros. Our specimen 

 proves to be Cichlosoma hedricJci, (Meek), de- 

 scribed by Dr. S. E. Meek in 1901- in his Fresh- 

 water Fishes of Mexico. 



No species of this family have ever reached 

 the New York Aquarium until the present sum- 

 mer when (about the last of June) six small 

 specimens arrived. These were purchased from 

 a boy who brought them all the way from Vera 

 Cruz. ]Mexico. in a two quart tin bucket. The 

 largest of the specimens at the time of arrival 

 was about two and one-half inches long. They 

 were placed at once in one of our balanced 

 aquaria where they have been ever since. When 

 the specimens arrived their colors apparently 

 were not fully developed, but they have grown 

 rapidly in capti\'ity and the colors have become 

 brilliant, especially in the males. 



Fresh water fishes are not so well known as 

 marine fishes for their ability to change their 

 colors. This species, however, exhibits this 

 phenomenon to quite a marked degree. The 

 chromatophores or color cells not only have a 

 remarkable range of contraction and expansion 

 of the color granules for a fresh water fish, but 

 thev are under such control of the nervous sys- 

 tem that they operate instantaneously. 



The ordinary background coloration of oliva- 

 ceous varies from dark olive to verj^ pale olive, 

 and this is often covered, especially on the 

 head, with 3-ellow, more or less bright. There 

 are about eight vertical dark bands on the body 

 besides four others across the top of the head 

 and nape, and a dark lateral band extends back- 

 ward from the opercle. There is also a dark spot 

 at the base of the caudal fin. All of these dark 

 markings vary exceedingly. Sometimes they 

 are very prominent and again almost wanting. 

 Frequently a prominent black spot appears sur- 

 rounded by a lighter area on the middle of the 

 side. The lateral band usually extends back to 

 this spot but it may extend to the base of the 

 tail or it may fade out until almost invisible. A 

 brilliant blue color appears on the opercle, about 

 the month and on the ventral fins, and this may 

 disappear entirely. The vertical fins and the 

 upper part of the body are beautifully flecked 

 at times with an irridescent metallic blue and 

 tliis may also vanish completely. 



There must, then, be at least four kinds of the 

 eliromatophores containing the yellow, green, 

 blue and dark pigments, and these are all sepa- 

 rateh' under the control of the nervous sj-stem, 

 since the color changes may involve any one 

 color onl^', or two or all at the same time. 



The majority of these color changes can hard- 

 ly be explained by assuming that they are adap- 

 tive to the surroundings. It is observed, how- 

 ever, that the fishes become almost imiformly 

 pale olivaceous, and suppress all bright and 

 striking colors and marks when frightened. 

 Tliis change probably renders them less con- 

 spicuous against the bottom and among vegeta- 

 tion in their natural environment and adds to 

 their cliauces for escaping when pursued by their 

 enemies. In the absence of positive evidence, 

 however, it is useless to speculate. 



A few of the cichlid fishes are herbivorous 

 and have chisel-like teeth for the purpose of 

 biting off vegetation, but the majority are car- 

 nivorous and have pointed teeth. Our species 

 belongs to the latter class, and will eat crushed 

 clam and meal worms with avidity. 



They are among the hardiest fishes in the 

 Aquarium, as far as crowding is concerned at 

 least, for they have thriven and grown well in a 

 small balanced aquarium. Tliougli they were 

 taken at a venture they have proved to be among 

 the most interesting small fishes of our collec- 

 tion. R. C. O. 



