REPRODUCTION. 591 



In this case they are termed gemmules instead 

 of buds. This mode of reproduction is exem- 

 plified in the Volvox, which, as we have already 

 seen, is an infusorial animalcule of a spherical 

 form, exhibiting incessant revolving move- 

 ments.* The germs of this animal are deve- 

 loped, in great numbers, in its interior, having 

 a globular shape, and visible, by the aid of the 

 microscope, through the transparent covering ; 

 and while yet retained within the body of the 

 parent other still minuter globules are developed 

 within these, constituting a third generation of 

 these animals. After a certain period, the young, 

 which have thus been formed, escape by the 

 bursting of the parent volvox, which in conse- 

 quence perishes. Similar phenomena are pre- 

 sented by many of the Infusoria. In some of 

 the Entozoa, likewise, as in the Hydatid, the 

 young are developed within the parent ; and this 

 proceeds successively for an indefinite number 

 of generations.^ In most cases of the spon- 



* Vol. i. p. 188. This animal is delineated in Fig. 79. 



t The mode in which infusory animalcules are produced and 

 multiplied is involved in much obscurity. Many distinguished 

 naturalists, adopting the views of BufFon, have regarded them as 

 the product of an inherent power belonging to a certain class of 

 material particles, which, in circumstances favourable to its ope- 

 ration, tends to form these minute organizations ; and in this 

 manner they explain how the same organic matter which had 

 composed former living aggregates, on the dissolution of their 

 union, reappears under new forms of life, and gives rise to the 

 phenomenon of innumerable animalcules, starting into being, 



