IKFtrSOKIAL ANIMALCULES. 53 



M. Pineau, in a second communication in 1848, gave the further 

 course of development, affii-ming that, at a certain period of their 

 existence, the Vorticclla undergo metamoiiihoses analagous to those 

 of insects ; that after having passed through a chiysalis-Hke state, 

 they give birth to an animalcule completely different from their 

 primitive form. (See family Vorticellina, Part III.) 



Without detailing all the changes recorded by Pineau, it may 

 suffice to state, he saw the Vorticellce lose then- pedicles, assume the 

 form of an egg-shaped globule, and eventually, he believes, become 

 converted into Oxytrichce. 



Doubting much, M. Pineau's hypothesis of the transformation of 

 formless organic particles into definite organic beings, we wovdd, 

 however, receive his statements concerning the metamorphoses of 

 animalcules with more readiness, inasmuch as many observers have 

 been led to believe in the reality of such ti-ansactions ; and we may 

 caU to mind that, according to Professor Baer, and his followers, 

 Lcuckhart and Rcichenbach, the Infusoria, as a class, have no 

 existence, but are merely embryonic forms of higher animals. 



That skilful English observer, Mr. BrightweU, of Norwich, also 

 believes that he has detected a cycle of changes in the Zoothamnium 

 arhuscuU, illustrative of Steenstrup's hypothesis of " alternation of 

 generations;" or of that of a 'spermatic force,' according to the 

 more philosophic inteipretation of such phenomena by Professor 

 Owen. (See Zoothamnium, Part III.) 



Most of the preceding account, of the reproduction of Infusoria, 

 applies especially to those of an undoubtedly animal nature, and 

 but partially to the doubtful organisms of Ehrenberg's families 

 Closterina and Bacillaria. The latter, besides propagating in common 

 with true animalcules by spontaneous fission, also do so by what is 

 called conjugation, a process peculiar to themselves. However, we 

 shall defer gi'S'ing an account of this interesting phenomenon, until 

 we especially consider the characters of those families exhibiting it. 



"We can now state that Wagner, " Zootomie" sect. Infusoria, 1848, 

 and Van der Hoeven, " Handbuch der Zoologie, 1850," agree with 

 Siebold and Dujardin in restricting the reproduction of Pohjgastrica 

 to fission and gemmation, that by ova being denied. All those named, 

 coincide, likewise, in opposing Ehrenberg's views of the contractile 



