484 Dr. A. Gruber on the 



experiment appeared capable of another interpretation. In 

 the small pieces separated from the anterior end the perfect 

 appearance on the following day was due not to regeneration, 

 but to simple wound-healing, in the course of which the 

 separated portion of the peristomial circlet had closed up into 

 a circle, and thus an illusory picture of a perfect Infusorian 

 was produced ; but a new mouth had not been formed when 

 the original one was left behind by the incision ; in short, 

 what had been lost was not replaced by anything new 

 (fig. 8 b). In the second case also we have not to do with 

 a regeneration, for in the middle part of the body of the 

 Stentor under experiment a new peristomial area with the 

 adoral zone of cilia was already in course of formation, and 

 the incision, which passed close in front of this rudiment, had 

 actually only divided the Stentor into two parts, which would 

 soon afterwards liave separated spontaneously from each other. 

 In the portion which had retained the original anterior end it 

 was only necessary for the wound to close up and the body to 

 taper again into the form of the hinder end; in the other tlie 

 wound also closed, and the accompanying rudimentary peri- 

 stome simply passed through its further course of development 

 until the formation of the perfect peristomial area and the 

 buccal spiral. From these observations therefore it only ap- 

 pears thai a process of wound-healing may occur in Infusoria 

 even without the presence of a nucleus^ and that a process of 

 new-fo7-7nation , ichen once in progress, may also continue 

 vnthout disturbance without the help of the tiucleus ; the impulse 

 thereto, as we shall see hereafter, has indeed proceeded from 

 the nucleus, but, this being once given, the impulsive element 

 may be removed without at tlie same time cancelling the 

 movement. At least I think that we cannot interpret the 

 second experiment, which I afterwards often repeated in the 

 same way, otherwise than that in the neiv formation of parts 

 in Infusoria we must see a movement lohich incessantly presses 

 toivards its object when it has otice been set going. But such a 

 movemeyit carmot be started, i. e. " orgamda " cannot be p>ro- 

 duced anew, when the nucleus is lost. This is proved with 

 certainty by the experiments which I will now describe. I 

 cut a small piece off a Stentor in such a manner that no part 

 of the peristomial circlet was separated with it, because this 

 might afterwards have led to mistakes, and I isolated it 

 (fig. 10) ; it was not regenerated, and on subsequent prepa- 

 ration it appeared that no constituent of the nucleus was 

 contained in it. I repeated the experiment, and again sepa- 

 rated from another individual a small portion, on which also 

 there was no trace of peristomial cilia (fig. 11) ; on the next 



