238 Dr. C. F. J. Lachmann on the Organization of Infusoria. 



the increase by fissation or gemmation, and that by embryos * ; 

 for the same animal which has pi'opagated vegetatively for a 

 time by fissation and bud-formation, and consequently performed 

 the functions of a nurse, may be seen subsequently playing the 

 part of a mother by the production of embryos ; nay, one animal 

 may at the same time increase by the vegetative process of fissa- 

 tion and propagate by the development of embryos, as is proved 

 to me by observations on Stentors. If an alternation of genera- 

 tions in the received sense should occur amongst the Infusoria, 

 it could only be in this way, that the very small embryos pro- 

 duced in the nucleus, or those to be mentioned immediately, 

 might be produced asexually, and even when sexually mature 

 might not increase vegetatively, but by sexual reproduction ; 

 but this supposition is totally unsupported, and even contradicted 

 by the observations on the Acinette. 



I may now be permitted to mention a mode of reproduction 

 which has hitherto been observed in but few cases, and even in 

 these not sufliciently to enable us to decide whether it is to be 

 regarded as a modification of the above-mentioned production 

 of embryos in the nucleus, or as an independent kind of propa- 

 gation. It has as yet been described only by Stein t in Vorti- 

 cella microstoma and nebulifera, and by Cienkowsky % in Nassula 

 viridis^. 



In these cases the reproduction was commenced by encysta- 

 tion, and then several large circumscribed bodies, probably en- 

 larged parts of the nucleus, made their appearance in the body, 

 which gradually became converted into a simple vesicle without 

 recognizable organs (the mother- vesicle, Mutterblase of Stein) : 

 these afterwards became elongated into processes, which broke 

 through the cyst, and bursting at the apex, allowed a great 

 number of small. Monad-like creatures to escape, which soon 

 dispersed themselves in the water. It was only in his most 

 recent observations on Vorticella microstoma, that Stein saw the 

 production of larger globules, " daughter-vesicles '' ( Tochter- 

 blasen), in the interior of the mother-vesicle; but previously he 

 had seen nothing of the kind : it must remain uncertain whether 



* Even if this were proved to be sexual reproduction. 



t L. c. supra. 



X Siebold and Kolliker's Zeitschr. vi. p. 301. In a note (4) on p. 301 

 of the Bulletin de I'Aead. de St. Petersb., Cienkowsky mentions the same 

 circumstance with regard to Nassula ambigua, Stein. I do not know 

 whether by this he refers to the same observations with regard to Nassula 

 viridis, alluded to above. 



§ Perhaps the reproduction of Chlorogonium euchlorum, described by 

 Weisse and Stein, also belongs here (unless it be a division into numerous 

 segments after a change of skin), and possibly the state of Acineta mysta- 

 cina represented by Stein on tab. 1. fig. 20 of his work. 



