474 Dr. A. Gmber on the 



the last century, upon the great sun-animalcule, Actino- 

 spluerium Eichhornii^ by its discoverer, Eichhorn himself; 

 afterwards, namely in 1862, on the same object, by Hackel ; 

 Greeff, in 1867, artificially divided* the Pelomyxa palustris, 

 which he described, and Hackel again made the same experi- 

 ments with his Myxastrum radians f. They all succeeded in 

 obtaining fragments capable of living on by the artificial division 

 of these Protozoa. In the same way botanists have separated 

 fragments from plant-cells, and indeed, as we shall have to 

 notice hereafter, from multinucleate cells, and by this means 

 have obtained small living individuals. 



In ciliated Infusoria, and therefore in unicellular animals 

 of com]:)licated structure, these experiments were first made 

 very recently, and indeed simultaneously, by M. Nussbaum 

 and myself. Nussbaum, whose observations were published| 

 before mine, operated with Oxytricha^ and showed that if such 

 an Infusorian w^as divided by a sharp cut longitudinally or 

 transversely into two parts, these were able, within a short 

 time, usually on the following day, to convert themselves 

 again into perfect animals, each half replacing the other defi- 

 cient one, the anterior end replacing the lost posterior end, 

 and vice versa ; smaller fragments also were capable of com- 

 pleting themselves again. 



For my part I have made use of another object in my ex- 

 periments, namely, the large Stentor cceruleus, which certainly 

 is not so resistent as Oxyfricha, and cannot be preserved alive 

 so long isolated ; but, on the other hand, from its larger 

 dimensions and its exceedingly characteristic mode of ciliation, 

 allows the course of the regeneration to be more easily and 

 distinctly watched §. 



In the first place, as regards small injuries, these heal very 

 rapidly, the cortical layer closing together at once over the 

 wound ; when the mutilations are more profound, on the 

 contrary, the Stentors often acquire a crippled form, which is 

 either not lost again or, as I have frequently observed, only 

 disappears quite gradiially. Thus a Stentor which had grown 

 deformed in consequence of a cut on one side, and had be- 

 come drawn out into an abnormal hinder extremity quite close 

 to the peristome, occupied eight days before it had again 

 become quite normal. 



* " Ueber Actinosph^rimn Eichhornii, &c.," in Arch, fur mikr. Anat. 

 Bd. iii. 



t " Monograpliie der Moneren," Jenaische Zeitsclir. fiir Naturwiss. 

 Bd. iv. (1868j. 



X Sitzuugsb. der niederrli. Gesellsch. fur Natiu"- und Heilkunde zu 

 Bonn, Sitzung. der med. Sect. 15 Dec. 1884. 



§ As previously stated (see Introduction) I have already made known 

 what follows in shorter communications. 



I 



