M. Balbiani on Sexual Reproduction in the Infusoria. 435 



XLIV. On the Existence of a Sexual Reproduction in the 

 Infusoria. By M. Balbiant*. 



The discovery of the propagation of the Infusoria by the pro- 

 duction of embryos or internal germs, which has already been 

 ascertained to prevail in a certain number of species belong- 

 ing to different groups, has opened a new field of research in the 

 history of the development of these animalcules. It has shown, 

 in fact, that besides the two truly agamic modes of reproduc- 

 tion, by spontaneous division and gemmiparity, previously ad- 

 mitted in this class, there exists a third mode, capable of a 

 very different interpretation, and which has at least this point in 

 common with the reproduction by embryos of the superior sexual 

 species, that, as in the latter, the young are formed in the inte- 

 rior, if not in a special cavity of the parent which gives them 

 birth. But no one has yet shown that the formation of the 

 embryos in the Infusoria was accompanied by any of the circum- 

 stances which indubitably characterize a generation accomplished 

 by the agency of distinct sexual apparatus. Stein was one of 

 the first to call attention to the part played by the nucleus in 

 this production ; but he thought that the germs were developed 

 on the surface of this body by a phsenomenon of gemmation, 

 which would assimilate them rather to bulbilli or caducous buds, 

 than to embryos originating from fertile ova. 



My own observations have led me to regard the origin of 

 these bodies in a different light ; I hope that I have been fortu- 

 nate enough to demonstrate that the phsenomena which accom- 

 pany their formation enter perfectly into the series of those 

 which, in the higher animals, are essentially characteristic of 

 sexual generation. As I cannot, in this note, dwell at any 

 length upon the facts which I have been enabled to observe, and 

 which already relate to six or seven species representing different 

 groups, I shall content myself with giving a rapid sketch of the 

 phsenomena relating to the embryonic reproduction of that species 

 in which I have been able to trace it most completely, — the green 

 Paramecium [Paramecium bursaria, Focke; Loxodes bursaria, 

 Ehrenb.). 



In this species, as in nearly all Infusoria, there exists a 

 nucleus, which is accompanied here by a small lenticular body, 

 usually lodged in an excavation of the nucleus, near one of its 

 extremities, and generally described under the improper name of 

 nucleolus. 



For several generations the Paramecia multiply by spon- 

 taneous scission, each of the two new individuals obtaining half 

 the primitive nucleus. Such is the very simple phsenomenon of 



* Translated from the ' Coraptes Rendus,' 29th March, 1858, p. 628. 



28* 



