184 METAMORPHOSES OF MAN 



The Infusoria are not reproduced by ova alone; 

 indeed, this is apparently their rarest form of propa- 

 gation, for it appears only after the other modes, and 

 these were known long before it. As early as the 

 year 1765, Charles de Saussure observed that they 

 multiplied usually, by a peculiar process of spontaneous 

 division, by which two individuals were produced, 

 which exactly resembled the single one from which 



that of the illustrious Jean Miiller (1856), referred to in the works 

 of Lieberkiihn, and Claparede and Lachmann. The two latter 

 made similar observations some short time after (1859). Both dis- 

 covered in the bodies of certain Paramecia, filaments which were 

 decidedly analogous with those in the fecundating element of all 

 animals. But neither of them determined the organ from which 

 they proceeded, and neither of them detected the peculiar move- 

 ments of these corpuscles. Nevertheless both admitted the possi- 

 bility of the union of the sexes in Infusoria, and this conclusion 

 was accepted by the Academy (" Eapport sur le grand Prix des 

 Sciences physiques pour l'annee 1857," by M. de Quatrefages). 

 M. Balbiani showed that the sexes were united in the Infusoria, 

 and that the enigmatical bodies which Siebold termed nucleus and 

 nucleolus, were really generative organs, distinguished by the pro- 

 ducts to which they gave rise. He described the modifications 

 which each undergoes when it enters upon its function, and he also 

 demonstrated the changes which take place in the ovum after 

 impregnation. Part of M. Balbiani's statements has been verified 

 by myself and the remainder has been accepted in its entirety by 

 M. Claparede, who, in the notes added in 1860 to his "Etudes sur 

 les Infusoires," renders ample justice to the valuable results arrived 

 at by M. Balbiani. The latter naturalist's writings have appeared 

 in the "Comptes Bendus," 1858 — 1860, and in the " Journal de la 

 Physiologie de l'Homme et des Animaux : " most of them have been 

 collectively published under the title of " Kecherches sur les Phe- 

 nomenes sexuels des Infusoires," 1861. On his part, Stein, who 

 has published many beautiful memoirs upon the history of Infu- 

 soria, appears to have arrived at results in accordance with those 

 of M. Balbiani (Claparede) ; but I regret to say I am unacquainted 

 with the work which he has just published. 



