100 THE BLACK GOBY. 



many of tlie more delicate began to grow sluggisli and 

 manifestly unliealtliy; some of the Fislies, of tlie 

 MolliiskSj particularly tlie nnivalves, and the smaller 

 Crustacea, died off one by one ; and the water began 

 to have a tainted odour, arising, as I discovered, from 

 the carcases of some of the animals that had died 

 beneath the shelter of the stones. 



The whole contents were therefore removed : the 

 plants and animals, — such of them, at least, as appeared 

 in health, — being temporarily placed in a pan, while the 

 water, sand, gravel, and clay were thrown away, the 

 interior of the tank well cleansed, and refilled with 

 new materials. With these I got on better ; though, as 

 it was always an object with me to have as many 

 animals under observation as possible, I did not care 

 to confine the number to such as would maintain the 

 balance with the plants. I preferred to change the 

 water periodically, as the sea flowed invitingly up to 

 the very door, and accordingly renewed it regularly 

 about once in three weeks. 



THE BLACK GOBY. 



This fish [Gobius niger), of which I had several 

 about three inches long, soon became tame, feeding 

 readily. After a few weeks they would come out of 

 their shelter as soon as a stick was put into the water, 

 and at length grew so bold as to snap at and seize 

 the stick. A little Two-spot Goby ( G. Ilutliensj)arr{) 

 elicited the cannibal propensities of his black cousin ; 

 for no sooner was the little creature put into the tank, 

 than presently the Black Goby caught sight of him, 

 and, rushing towards him, seized him by the tail, 



