64 THE VICTORIAS NATURALIST. 



not deposit an egg, unless it retains vitality, like some rotifers, 

 even when the mud containing them holds but little moisture ? 

 This was the form I exhibited on our last evening, but regret 

 being unable to procure any for this evening, as the pond in 

 which there was a great abundance failed to yield any on my last 

 visit. 



Before mentioning the further captures made at the same time, 

 I may perhaps, for the sake of such of our members as may not 

 be acquainted with these forms of life, say a few words on the 

 rotifera generally. They are a class of very numerous organisms 

 inhabiting water. Their diversity of form is extreme ; one 

 characteristic is common, namely, they all possess cilia of some 

 kind about the head whereby they propel themselves through the 

 water or create minute whirlpools which bring their prey within 

 reach. This peculiarity has obtained for them the appellation 

 "wheel animalcules." Their classification has been a matter of 

 dispute, and at the present time they are classed with the worms. 

 Compared with the infusorians with which they are commonly 

 found associated, they are of high organization, having a com- 

 plicated masticating apparatus ; stomach furnished with glands, 

 supposed to represent the liver ; a system of water circu'ation 

 throughout their bodies ; traces of a nervous system ; an 

 elaborate arrangement of muscles, chiefly concerned with 

 manipulating the mouth organs ; and specialized reproductive 

 organs. Among them there are forms destitute of means of 

 prehension (as Asplanchna brightwertii), and are thus ever swim- 

 ming to and fro ; others, possessing a foot, sometimes — con- 

 veniently for the observer — remain attached by it, and thoroughly 

 exhaust the water in the vicinity of all particles acceptable to 

 them, which, being done, detach themselves and sail away to 

 other fields ; others there are which cannot swim, but remain 

 attached to one place, and must content themselves with such 

 nutriment as currents bring within the influence of their vortex- 

 creating cilia. These include some of the most beautiful forms, 

 such as the tube builders, whose cylindrical residence is in some 

 species built up of little pellets, shaped by a special organ out 

 of the particles obtained along with the food ; while in others — 

 which as compared with the last-mentioned are as builders of 

 a mud hut to a bricklayer who makes his own bricks as well as 

 lays them — the tube is plastered together in a homogeneous mass 

 like the stucco on a wall. The free swimmers contain some 

 genera encased in glassy armour ; and others, with soft integu- 

 ment, occasionally crawl, looping their bodies after the manner 

 of the caterpillars known as geometers. Their mode of repro- 

 duction differs among the rotifera, some carrying the egg until 

 it develops into the perfect animal, when they issue forth into 

 their little world fully equipped for the struggle for existence. 



