204 POPULAR HISTORY OF THE AQUARIUM. 



but when touched or shaken thej immediately again with- 

 draw themselves within their sliell, and remain motionless. 

 " This inabiHty to swim is no doubt owing to the want of 

 those pencils of long hairs or filaments which adorn the su- 

 perior and inferior antennae of the Cyprides, and which we 

 have seen are the organs by which they swim.""^ 



From an observation made by Dr. Baird following the 

 above quotation, it is evident that when it was written the 

 means had not been discovered of keeping salt-water in a 

 state fit to sustain life in marine animals. That gentleman 

 states that the rapidity with which salt-water, when kept in 

 a small vessel in a room, became putrid, was so great that 

 he could not extend his information so much as he could 

 have wished ; at the same time expressiug an opinion that 

 '^ the labours of any inquirer after them would assuredly be 

 rewarded with much success." Now that such facilities are 

 afi'orded for inquirers, by means of Aquaria, surely some ^vill 

 be found to take up this family and complete its natural 

 history. 



Cyclops quadricornis 



Has a horny covering, and is something like a tadpole in 

 shape, with one eye and a long plated tail. The female 



