4X8 THE HISTORY OF BIOLOGY 



and other works of his was that the number of known Infusoria was consider- 

 ably increased, and their classification essentially advanced. Anguillulidas 

 and cercaria, which had hitherto been counted amongst them, were excluded, 

 the Rotatoria were separated, and the genus- and species-diagnosis pre- 

 cisely defined, many of them still holding good. The whole of this careful 

 and praiseworthy work, however, Ehrenberg used in support of an utterly 

 unprofitable theory; starting from the then prevalent belief in one single 

 primal type for all animals, he tried to discover in the Infusoria the same 

 organs as in the higher animals; the vacuoles that are visible in the Ciliata, 

 and which partly alter shape, were seen in his imagination to possess canal- 

 shaped outlets and were thus made the basis of an artificially ramified di- 

 gestive system; he believed he had found sexual organs and eggs in the objects 

 he investigated — in a word, they were to his mind, as the title of his work 

 indicated, "complete organisms." That he entirely rejected the belief in the 

 spontaneous generation of such creatures is self-evident; indeed, this dis- 

 belief in the spontaneous-generation hypothesis may have been firmly rooted 

 in him before he began to study the Infusoria and perhaps contributed in 

 some degree towards inducing in him these efi^orts at finding in them as 

 complete a form as possible. His theory won many adherents among his 

 contemporaries — it was embraced, inter alia, by Owen in his earlier works; 

 when eventually it was exploded, Ehrenberg, after spending some years in 

 vainly defending his cause, withdrew entirely from all research work. 



The scientist who from the outset came forward as a decided opponent 

 of Ehrenberg and who rapidly won a victory for his views was Felix Du- 

 jARDiN (i8oi-6i), professor first at Toulouse, then at Rennes. In certain of 

 his works, the last and most comprehensive of which is dated 1841, he laid 

 the foundations of a new conception of the Infusoria. He achieved this first 

 of all by incorporating with them a category of still lower organisms, which 

 he made the subject of special investigation, namely the Rhizopoda. These, 

 which include types without any external organs, and indeed without any 

 definite external bodily form, offered the best possible proof against the 

 lowest animals' acceptance as "complete organisms." Dujardin found that 

 both these and the higher Infusoria consist of a homogenous mass, which 

 possesses the power of absorbing nourishment, contracting and moving, and 

 reacting to external impressions. This mass he called "sarcode,"a name that 

 \yas at one time used, especially in France, to denote that fundamental sub- 

 stance of which living creatures in general are built up, until it was sup- 

 planted by the word "protoplasm." In the sarcode Dujardin found vacuoles 

 and granules, but no permanent organs, and the cilia; that cover the body 

 of the higher Infusoria possess in his view no affinity with the hairy forma- 

 tions of the higher animals. In all this Dujardin stood undeniably on surer 

 ground than Ehrenberg; on the other hand, he failed to elucidate the 



