466 Dr. R. Greef on the Structure and 



animalcule now adheres to the side walls of the other, for 

 which purpose a position on the hinder part of the bodj, 

 nearly corresponding to the bottom of the body-cavity, is 

 generally selected (PI. XIII. fig. 2). 



After a short time the smaller Vorticella adheres firmly to 

 the larger one, so that, if the process has not been traced, one 

 supposes one sees a bud-formation. By careful examination, 

 especially with the aid of cautious compression, we now make 

 the further interesting observation that the conical base which 

 was at first retracted to form the sucking-pit is again ex- 

 tended, and serves as an organ for boring into the subjacent 

 side wall of the larger Vorticella (PI. XIII. fig. 3). The 

 conical process thus formed gradually penetrates deeper and 

 deeper ; and this is the introduction to a complete amalgama- 

 tion of the two individuals. The intervening walls are ab- 

 sorbed, and soon there is an unobstructed communication 

 between the two body-cavities. The pressure exerted in 

 this process is so strong that we frequently see clear, bead- 

 like drops of parenchyma make their appearance at the 

 margin of union (PL XIII. fig. 4). The bud-like structure 

 now contracts or shrivels more and more, its contents being, 

 as it were, sucked up by the large Vorticella ; so that finally 

 there is only left on the side wall a tubercle with a small 

 external aperture, the contours of which pass directly into 

 those of its bearer, and in which we can no longer recognize 

 the Vorticellan form and organization. In this way in course 

 of time the whole contents of the small Vorticella pass into 

 the larger one ; and at last only a more or less thin lobe pro- 

 jects from the wall of the latter, evidently the contracted and 

 shrivelled empty skin of the former bud-like individual 

 (PL XIII. fig. 6,k), This lobe is usually apparently beset 

 all round with fine hairs or bristles, which, however, are 

 probably only the expression of the numerous foldings of 

 the originally annulated integument. Finally the lobe itself 

 is constricted off, and often remains connected with its sup- 

 porter only by a thin tenacious filament (fig. 7,k), until this 

 also is torn by a sudden jerking back of the Vorticella, and the 

 lobe is cast off, by which the process of amalgamation of the 

 two individuals is completely finished. 



I must expressly remark that, notwithstanding I have 

 repeatedly sought for them, I have never observed in this 

 marine Vorticellan the so-called rosettes of fissional scions 

 produced by rapidly continued division, but always only 

 bifissions, although these, singularly enough, are remarkably 

 frequent in combination with the bud-like amalgamation. It 

 is, therefore, not to be supposed that the smaller individuals, 



