Objection of Anuclear Regeneration in S tent or 55 



istomal, ciliated area, and he divided it in two halves. 

 Since in this stage the chief nucleus, ordinarily monili- 

 form, contracts into a round or bean shaped mass, 

 Gruber was able to remove it completely from both 

 halves. The division of the animal was effected in such 

 a way as to produce about the same two halves as would 

 later have been produced by spontaneous division. In the 

 fragment which contained the original peristome the 

 simple cicatrization of the wound was enough to repro- 

 duce a complete individual. In the other fragment which 

 contained the posterior extremity the wound closed in 

 the same way and the anterior extremity continued its 

 development until the peristomal area and the buccal 

 spiral were completely formed. 28 



This result seemed to contradict the view that the 

 formative action of a nucleus, as .a developmental center 

 for the unicellular organism, was exerted continuously 

 throughout the whole duration of development. But the 

 following considerations show that this premature con- 

 clusion is quite fallacious. 



We should remember in this connection another ob- 

 servation of Gruber. He cut off from the anterior end 

 of a Stentor a fragment absolutely without a nucleus, but 

 containing a small portion of the peristomal band. The 

 cicatrization of the wound was followed by the ordinary 

 contraction of the fragment and thereby the small portion 

 of the peristomal band was given the appearance of a 

 complete Infusorian such as would be formed by regen- 



28 Gruber: Uber kiinstliche Teilung der Infusorien. Zweite 

 Mitteilung. Biol. Centralbl. Band, V, No. 5; May i, 1885. P. 139 

 140; und : Beitrage zur Kenntnis der Physiologic und Biologic der 

 Protozoen; Berichte der Naturforschenden Gesellsch. zu Freiburg 

 j. B., Freiburg i. B., Mohr, 1886, P. 1314. 



