IIEYIEWS. 



On True Sexual Reproduction in the Infusoria. — Recherches 

 sur les phenomenes sexuels cles Infusoires. Par le Docteur 

 Balbiani, 1861.^ 



The Infusoria have long bceu known to mnltiply by spon- 

 taneous fission, external germination, and the production, 

 internally, of variously formed bodies, which many observers, 

 somewhat hastily, have described under the name of " em- 

 bryoes." The phenomena of "encysting," "conjugation,'" and 

 "alternate generation" (so called), which these animals fre- 

 quently exhibit, and the relation, real or supposed, between 

 such processes and their various modes of propagation, have, 

 from time to time, afforded subject-matter for not a little 

 controversy. Stein's theory of Acinetism, once universally 

 received, then skilfully assailed by Lachmann and Cienkowsky, 

 and again defended by D'Udekem, has now virtually been 

 abandoned by its distinguished author. But, although some 

 knowledge was gained, and many false notions dispelled by 

 these and other investigations, it is surprising how little, 

 before 1858, had really been done towards proving the occur- 

 rence among the Infusoria of a true reproduction, similar to 

 that which takes place in all the higher classes of animals. 

 An English anatomist had, in 1851, I'ecorded the presence of 

 ova and spermatozoa in one of the marine sponges [Tethya], 

 thus, for the first time, showing that the Protozoa formed no 

 exception to the four remaining sub-kingdoms of animals iu 

 the possession of these essential elements. Five years later 

 his observations were corroborated by Lieberkiihn, in the 

 case of the fresh-water sponge {Sponyilla). Even then, the 

 existence of generative elements still remained to be demon- 

 strated in the Infusoria — a class which might well be con- 

 sidered as ranking above sponges in the scale of organisation. 

 Ehrenberg, it is true, had described their " nucleus" as a male 

 organ — an opinion which received a qualified support from 



* Published, with tiiree plates, in torn, iv, of Dr. E. Bro\yii-Scqiiaicrs 

 ' JouriKil do la Pliysiologie,' pp. 102, 194, 431, and 405. 



