312 MR. HANCOCK ON THE NIDIFICATION OF 



that is at present known on the subject, and its accuracy can be 

 verified by any one who will take the trouble to look into almost 

 any pool of water during the summer months, — the breeding sea- 

 son of the Stickleback. At this time these fish will be observed 

 near to the margins, busily engaged in building and guarding 

 their nests ; and shoals of the fry may be seen, in different stages 

 of development, swimming about in all directions. But if we 

 wish to study, to advantage, the nidifictaion of this species, a few 

 specimens should be placed in confinement about May or'June ; 

 and then all their movements can be narrowly watched and accu- 

 rately observed. Care must be taken, however, that they be left 

 unmolested, and that their new abode resem.ble, as much as pos- 

 sible, their usual haunts. I have lately had an opportunity of 

 noticing the habits of this fish, during the breeding season, under 

 the above favourable conditions. 



We have, for some time past, kept a glass trough filled with 



aquatic plants and animals ; the bottom of this vessel is covered 



with mud, and the rock- work, piled up in the centre, is overgrown 



with a delicate hair-like Conferva j a few floating plants spread 



over the surface of the water, and innumerable Entomostraca, 



and other small Crustaceans, as well as various animalcules, 



swarm in all parts ; the minute, but deadly, poison-armed Hydra 



also prevails where food is so plentiful ; and a solitary individual 



of the great water beetle, Dytiscus marginaius, rambles over its 



wateiy domain, lord and master of all. Several of the freshwater 



Mollusca also people the trough, which on the whole has much 



the appearance of a miniature pond. Into this new home were 



put four or five sticklebacks last May ; and they, at once, made 



themselves perfectly at ease. One, without the least hesitation, 



took possession of a certain spot, which it guarded with the 



greatest pertinacity, attacking vigorously any of its companions 



that might happen to approach the chosen locality. The beetle 



too, which sometimes came slowly paddling by, was pounced upon 



and unceremoniously tumbled over ; but secure within his scaly 



armour, as the knights of old, he little heeded the onslaught of 



his naked assailant ; so overpowering all opposition he scrambled 



onward in his undeviating path. 



