254 GENERAL HISTORY OF THE INFUSORIA. 



in which the membrane was not plicated, but loosely enclosed the Podophrya 

 like a sac, I noticed that the peduncle of the cyst was continued uninterrupt- 

 edly into the membrane, of which consequently it must be regarded as a pro- 

 trusion, and that it had no connexion whatever with the original slender pe- 

 duncle of the Podophrya itself. In fact, I noticed cysts in which this original 

 slender peduncle was appended to the saccular envelope. I am unable, there- 

 fore, to adopt Stein's view that the Podophryce are enclosed in a membrane, 

 of which the slender peduncle is simply a tubular protrusion. This is true 

 only with respect to the short peduncle of the encysted Podopliryce. 



" What afterwards becomes of the cysts I have been unable, in spite of ob- 

 servations continued for months, to determine." 



Multiplication by Spontaneous Division seems now to be sufficiently de- 

 monstrated. Ehrenberg and other earlier writers, indeed, mentioned the 

 occurrence of self-fission ; but their accounts were too uncertain and inde- 

 finite, and strong doubts prevailed whether they had actually witnessed that 

 process, or the act of conjugation, to be presently noticed. Mr. Brightwell 

 appears {Fauna Infusoria of Norfolk) to have confounded the two processes ; 

 for he says — " They multiply by division, so that two and sometimes three 

 individuals are seen adhering together by theii' outer edge — the middle one, 

 the parent, being the largest," — an explanation inconsistent with the process 

 of fission as generally understood. Claparede states distinctly that he has 

 seen the act of fission ; "Weston describes it in Actinoplirys, and Cienkowsky 

 in Podophrya. " With regard to the reproduction of Actinophrys Sol/' writes 

 Mr. Watson (op. cit. p. 119), " I can positively affirm that self-division is 

 one mode ; for I may say I have witnessed it a hundred times and shown it 

 to others .... First was noticed a deep depression above and below, not far 

 from the centre of the body ; this, as it increased, threw the tentacles across 

 each other, in a manner similar to that described by Kolliker, when in the 

 act of inclosing an object of prey. This crossing, however, in the act of self- 

 division would appear to be only the necessaiy consequence of the depressions 

 alluded to, and the position into which the outer membrane (in which the 

 tentacles are inserted) is drawn. As division proceeded (XXIII. 31), the 

 two animalcules steadily, but rather quickly, increased the distance between 

 them, until the connecting medium was apparently a long membranous neck, 

 which, to my unpractised eye, appeared composed first of four, then of three, 

 then two irregular lines of cells (possessing no nuclei), which ultimately di- 

 minished into a single cord composed of three simple cells elongated like the 

 links of a chain, this becoming gradually more attenuated, imtil the exact 

 moment of its division could not be seen. All this latter portion of the pro- 

 cess was rather rapidly performed, — that is, from the first formation of the rows 

 of cells to the time of what I supposed to be the final separation, occupied 

 only about a quarter of an hour .... During the whole of the process, the valve 

 (^. e. the expanding and contracting superficial vacuole) of each segment, situ- 

 ated at nearly opposite extremes, was in constant action, and each creatui-e 

 Avas busily employed seizing its food." On following one segment after its 

 separation, " a floating faint line, the broken thread " (of connexion), extended 

 from it; and two of the cells, formerly contained within this bond, were attached 

 to its side, but were in a few minutes drawn into the body of the Actinophrys, 

 which there assumed a perfectly normal character. In Podophrya the process 

 of fission is similar (XXIII. 34) ; at first an annular constriction displays it- 

 self, and so rapidly deepens, that in an about half- an -hour complete trans- 

 verse fission is effected. The history of the segments is thus portrayed by 

 Cienkowsky (ojd. cit. p. 98), about ten minutes after the commencement of the 

 act of division: — "The upper segment had assumed an elongated form, was more 



