THE BLACK GOBY. 107 



many of the more delicate began to grow sluggish and 

 manifestly unhealthy ; some of the fishes, some of the 

 mollusks, particularly the univalves, 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 

 vt ater periodically, as the sea flowed invitingly up to 

 the very door, and accordingly renewed it regularly 

 about once in three weeks. Hence this must not be 

 considered as evidence pro or con on the philosophy 

 of the subject, a question which Mr. Warington's 

 experience triumphantly settles. 



THE BLACK GOBY. 



This fish (Oohius niger), of which I had several 

 about 3 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. EuthensparriJ , elicited the 

 cannibal propensities of his black cousin, for no 



