Balbiani on the Reproduction of Infusoria. 465 



Ehrenbergian types, Oxytricha, Stylonichia, Kerona, and 

 Urostyla, exhibits this arrangement in its greatest simplicity." 

 In this division of his subject M. Balbiani describes what is 

 commonly considered to be the mouth of Trachelitis ovum as a 

 generative aperture. 



M. Balbiani considers that species have been erroneously 

 made on account of the appearance presented by the ovary at 

 different epochs. He says, " Since my observations on the 

 singular transformations which the ovary of the infusoria under- 

 goes during the spontaneous division of those, animals, it is 

 evident that one phase of these transformations is characterized 

 by the elongated ribbon-like aspect which this gland assumes, 

 shortly before it divides itself between the two new individuals. 

 In this respect the ovoid and moniliform nuclei behave in pre- 

 cisely the same way, and recall for the moment, under this 

 aspect, the form which this gland presents among the vorti- 

 cellids and other types previously mentioned. These modifica- 

 tions, transitory and purely physiological, have more than once 

 been taken by classifying authors for permanent forms, and 

 employed under this idea for the characterization of certain 

 species. It is thus that under the name of Stentor Roeselii, 

 Ehrenberg describes an animalcule which differs from all others 

 of the same genus by its testicle (ovary) which takes the shape of 

 along sinuous band destitute of articulation, while amongst the 

 other stentors it is usually disposed as a chaplet. To this pecu- 

 liarity we must reduce the difference which Ehrenberg esta- 

 blishes between this species and S. Mulleri It is only 



necessary to look at his four figures of S. Roeselii to be satisfied 

 that two of them refer to specimens observed at the moment 

 of spontaneous division. As to the others it is probable that 

 they also relate to individuals about to divide themselves, but in 

 whom the signs of this process, and especially the existence of 

 a longitudinal ciliary crest, which is the first indication of it, 

 had escaped the celebrated microscopist.'" 



Let us now pass to the mode of fecundation, under which 

 title we read, " The facts by which I was led to study the pheno- 

 mena of the propagation of these animalcules, have received 

 from all the naturalists and physiologists of our epoch, a signi- 

 fication entirely different from that which I assign to them. All 

 these authors in fact see only a longitudinal self-division in the 

 appearance which I shall demonstrate to arise from the sexual 

 union of two individuals, and admit in consequence that the 

 greater part of' the species of this class are able to multiply 

 indifferently by transverse or longitudinal fission. The favour 

 with which this opinion — so little conformable to the real state 

 of things — has been received, and generally accepted as one of 

 the best ascertained facts of science, has induced me to describe 



