488 Dr. A. Gmber on the 



from the drawings which that naturalist was kind enough to 

 send me. Notwithstanding the small size and often very 

 irregular distribution of these structures, it seems to me very 

 probable that they must be regarded as subsidiary nuclei. 

 But this can be said with perfect certainty only when we have 

 succeeded in tracing their behaviour during the division and 

 conjugation of the Stentors. As regards regeneration, I 

 could discover no sort of influence that they were able to 

 exert upon that process. 



Observations upon the Spontaneous Division of the 

 Infusoria. 



So far as I know, no experiments have been made in order 

 to ascertain whether in the multiplication of the Protozoa by 

 division there exists any regularity as to the time in which 

 the divisions follow one another, whether a definite number of 

 divisions occur between two periods of conjugation, whether 

 the occurrence of division is caused by increased nourishment 

 and the growth consequent upon this, or, on the contrary, by 

 unfavourable external circumstances, or whether it is not at all 

 the consequence of external impulse, but is governed and pro- 

 duced by internal causes. These and many other questions 

 are still unanswered, and even the experiments which have 

 been undertaken for their solution have at present made only 

 a slight commencement, so that they can make no claim to 

 completeness, seeing that they have not furnished the oppor- 

 tunity of completing them by more ])erfect ones. Stentor 

 cceruleus again served me as my chief object of experiment ; 

 I had it in abundance at my disposal, and from its consider- 

 able size it could be easily isolated and watched. 



One series of experiments consisted in isolating Stentors, 

 and indeed, if possible, such as were just about to divide ; when 

 the division took place the daughter-individuals were separated 

 and observed by themselves, in order to see how and when 

 their division into grandchildren took place. It appeared 

 that this took place^ in most cases, simultaneously in the 

 daughter-individuals, although they were kept in separate 

 glasses. By "simultaneously," however, I do not mean that 

 the division takes place in both Infusoria at the same moment, 

 but perhaps within an hour or in the course of a few hours, 

 but at any rate on the same observation-day, which I will 

 reckon as from 9 a.m. to 4 p.m. Very often also the isolated 

 individuals divided during the night, and in the morning I 

 found both daughters divided into two granddaughters. The 

 small differences of time which occur between the divisions of 



