Natural History of the Vorticellae. 467 



which, however, are sometimes but little inferior in size to 

 those selected for union, had proceeded from simple bifission 

 without rosette-formation. Moreover I have not observed 

 the action on the nucleus described by Stein in this form, but 

 have limited myself to the above-described external phe- 

 nomena of the act of union. 



In freshwater Vorticellse, however, especially from the 

 Poppelsdorf Castle-pond near Bonn, I had abundant oppor- 

 tunity of observing both the rosette-formation of the fissional 

 scions and the internal processes arising from the gemmiform 

 amalgamation. In the first place, it was again in an animal- 

 cule belonging to the genus Vorticella {Vorticella campanula'^) ^ 

 which is characterized by a comparatively large body and an 

 unusually long peduncle (PL XIII. fig. 8), that I found many 

 gemmiform unions. In that represented in fig. 8 an open 

 union of the two body-cavities and a complete external 

 amalgamation had already occurred. The body-cavity of 

 the smaller Vorticella {¥) was filled with oval, sharply con- 

 toured, dimly shining corpuscles which passed through the 

 interior with a brisk skipping motion^ and also repeatedly 

 passed over into the larger Vorticella. I could not perceive 

 a nucleus in the gemmiform appendage. The body-cavity of 

 the other individual, however, was filled with comparatively 

 large corpuscles, also of an oval form and sharply circum- 

 scribed, which strikingly resembled hard-shelled ova. Here 

 also I could perceive no nucleus. It seems probable, there- 

 fore, that, in accordance with Stein's observations, we may 

 regard the two different bodies in the bud-like individual 

 and its supporter as produced by the breaking up of the nucleus 

 in consequence of the " gemmiform conjugation." I have 

 been unable, however, to observe any further development of 

 these bodies, as material of the same Vorticella^ afterwards 

 obtained, showed no trace of gemmiform unions. 



The remarkable rosettes^ and the bud-like individuals which 

 separate from them and unite with the larger Vorticellas, were 

 first of all repeatedly observed by me in Epistylis flavicans. 

 The rosettes occm-red as groups of from four to eight indi- 

 viduals ; and we may often see several rosettes at the same 

 time upon one stock (PI. XV. fig. 1, r^r^r^r). The groups 

 often remain together in the form of a rosette without being 

 in direct, firm union either with each other or with the stock, 

 their conical bases converging towards one another, and being 

 held in companionship by constant undulation of the posterior 

 circlet of cilia. Besides these, I also met with many gemmi- 

 form unions, but without succeeding in observing the internal 

 phenomena possibly connected therewith. 



