548 REPRODUCTION OF POLYGASTRIC 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. It does not appear that 

 the Polygastric Animalcules are usually capable of retaining 

 their vitality when dried up, as some of the Rotifera are known 

 to do ( 859). But it is unquestionable that their ova or germs 

 are susceptible of this treatment without injury ; and in this 

 manner they are probably carried about, in the form of minute 

 particles of dust, ready to develope themselves in any spot which 

 may afford 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). 



1126. The extraordinary powers of reproduction possessed 

 by these 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 ( 1128), 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^trans verse (Fig. 626, >), 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. By these 

 methods, sometimes employed singly, occasionally in combina- 

 tion, a single individual may soon become the parent of an 

 immense population. Thus the Paramecium aurelia, if well 

 supplied by food, has been observed to divide itself every twenty- 

 four hours ; so that in a fortnight, allowing the product of each 

 division to multiply at the same rate, 16,384 animalcules would be 

 produced from the same stock ; and in four weeks, 268,435,456 

 new beings would result from a continued repetition of the pro- 

 cess. But this animalcule has occasionally been observed to 

 increase with much greater rapidity ; the first million being pro- 

 duced (according to calculation based on fair data) within seven 



