552 REPRODUCTION OF INFUSORIAL ANIMALCULES. 



of the animal or vegetable particles, which thus consisted, as it 

 were, of their latent germs. But this hypothesis is unnecessary 

 to account for the phenomena ordinarily observed ; and it is 

 inconsistent with ascertained facts. Many of the Infusoria have 

 the power of inclosing themselves in a firm cyst, and they avail 

 themselves of this mode of protection when the pools in which 

 they have been living are dried up by the heat of the sun. By this 

 means they are enabled, like the Rotifera ( 931), to support 

 drought without injury ; and in this manner both they and their 

 germs are probably carried about, in the form of minute particles 

 of dust, ready to develope themselves in any spot which may af- 

 ford them the requisite moisture and nutriment. In this respect 

 they probably resemble the Fungi, whose germs are known to be 

 thus diffused (VEGET. PHYSIOL. 50 64). 



1214. The extraordinary powers of reproduction possessed 

 by th se Animalcules, will fully account for their rapid multi- 

 plication, when once they have obtained the means of develop- 

 ment. Several modes of propagation are observed among them. 

 Not unfrequently we observe, as in the Vorticella ( 1217), a 

 reproduction by buds developed from the side of the body, as in 

 the Hydra. In other species, again, the process of generation 

 is accomplished by the separation of the body into two parts : 

 the division, which may be observed in several stages of its pro- 

 gress, is sometimes transverse (Fig. 728, b\ sometimes longitu- 

 dinal (c), sometimes oblique. In other tribes propagation takes 

 place by ova or germs evolved within the body of the parent, 

 the greater part of whose bulk is often made up by them. Fre- 

 quently the Animalcules secrete a gelatinous matter from their 

 surface, which hardens and becomes a sort of cyst, within which 

 a division of the substance of the body takes place, a portion of 

 the nucleus going into each segment ; or the nucleus itself alone 

 breaks up into numerous germs. According to some observa- 

 tions made by Professor Stein, which, however, have since been 

 disputed, some of the most highly organised Infusoria (the 

 Vorticellce) give rise to animals which resemble the Rhizopoda 

 in their power of throwing out gelatinous filaments from various 

 parts of their bodies, and these again produce young Vorticellce 



