448 



THE MICROSCOPE. 



extremity, and presenting at the opposite end a distinct 

 mouth. Within this young animal, whilst still inclosed in 

 the body of its parent, we see a distinct nucleus, and the 

 usual contractile space of the full-grown creature. When 

 mature, the offspring tears its way through the membranes 

 inclosing the Acineta, which, however, immediately close 

 again. The latter continues protruding and retracting its 

 filaments, and soon produces in its interior a new nucleus, 

 which in its turn becomes metamorphosed into a young 

 Vorticella. 

 The same faculty of enclosing themselves in a cyst is 

 said to be made use of by the Vor- 

 ticella, as a means of self-preservation 

 if the water in which they have been 

 living dries up. When the animal is 

 thus encased, the mud at the bottom 

 of the pool may be baked quite hard 

 in the sun without doing it the least 

 injury ; and in this state the creatures 

 are often taken up by the wind with 

 the dust which it raises from the sur- 

 face of the parched ground, and borne 

 along to great distances, so as to cause 

 their appearance in most unexpected 

 loocalities (they are frequently found in roof gutters), where 

 the first shower of rain calls them back to active life. 



Conochilus vorticella, 1 belonging to the family iEcistina, 

 Plate III. No. 80, is one of the most remarkable and in- 

 teresting Rotifers met with. It is found in compound 

 groups of a whitish globular form in shallow ponds about 

 London. On Hampstead Heath a good supply is often 

 obtained throughout the summer months. The group 

 consists of from twenty to thirty, or more, animals, of about 

 twice the size of the full-grown volvox, and, like the 

 latter, can be readily seen actively rolling about when the 

 collecting-bottle is held up to the light. The colony ^is 

 attached to a centre disc, resembling a wheel with its 

 naves and spokes. The foot-stalk is three or four times 

 the length of the body, and has a somewhat spiral form, 

 which it contracts at pleasure, drawing the body down in 

 an instant close to the axis, although it does not appear to 



(1) Commonly called "olvor. but this is an error, as it clearly does not belong 

 to the Volvocime. 



Fig. 227. 

 Vorticella microstoma. 



