JS2 THE CELL 



irritability, reacting to mechanical, galvanic, and chemical stimuli 

 by contracting their bodies. 



According to Verworn, Ciliafa, too, which have developed 

 special locomotive organs, such as cilia, flagella, cirrhi, etc., 

 assume, when cut up, a complete autonomy and independence of 

 the nucleus. 



In Lacrymaria, each part, when deprived of its nucleus, ex- 

 hibits, after its separation from the body, the same movements 

 as it was performing before. Small portions of Stylonichia, 

 which are furnished with a number of ventral cilia, continue to 

 make with them the movements peculiar to their species. Even 

 the minutest portion of protoplasm, which is furnished with only 

 one bristle-like cilium, continues to make with it characteristic 

 movements. If it was directed backwards, it is suddenly from 

 time to time jerked forwards, by which movement the portion 

 receives a short jerk backwards ; thereupon the cilium returns 

 again to a state of rest, and so on. 



The contractile vacuoles of the Protista are, like cilia and 

 cirrhi, remarkable for complete autonomy. Even in non-nucleated 

 portions they can be observed to contract rhythmically for davs 

 together (Verworn). 



Finally, an important difference is noticeable between non- 

 nucleated and nucleated portions, as regards digestion. Whilst 

 small Infusoria, Rotifera, etc., are normally digested by nucleated 

 portions, in non-nucleated parts digestion is considerably dimin- 

 ished, both as regards time and intensity. It may, therefore, 

 be concluded that protoplasm can only produce digestive secre- 

 tions with the assistance of the nucleus (Hofer, Verworn). 



It is not surprising that diversities of opinion, as mentioned in 

 Chapter VII., should exist upon this subject, when the difficulty 

 of the problems to be solved be taken into account. 



Literature VIM. 



1. Balbiani. Recherches experimentales sur la merotomie des Infusoires cilies. 



Prem. part. Recueil. Zool. Suisse. 1889. 



2. Boveri. Ein geschlechtlick erzeugter Organismm oline mutter liche Eigen- 



schaften. Gesellsch. f. Morphol. u. Pysiol. zu Milnchen. 1889. 



3. Gruber. Ueber die Einjltisslosigheit des Kerns auf die Bewegung, die 



krnahrurig u. das Wachsthum einzelliger Thiere. Biolog. Centralblatt. 

 Bd. III. 

 Gruber. Ueber kunstliche The Hung bei Infusorien. Biolog. Centralbl. 

 Bd. IV. u. V. 



