XII 



rotations which Rossbach observed during his ex- 

 periments on the influence of some toxic substances 

 on infusoria. It is well known that in prepara- 

 tions infusoria will often be seen rotating in this 

 manner without any visible motive. According to 

 the above observation I have no doubt that these 

 rotations always are a symptom of indisposition? This 

 interpretation is also confirmed by the fact that 

 such rotations sometimes appear in the agonies of 

 death, thus I have seen infusoria turn rapidly round 

 their axes as often as 70 times immediately before 

 dying. 



c. The cause of death seems to be immaterial to this 

 chemotaclic action. It is found in dead bodies of 

 infusoria whether killed by faintly heating, by ebul- 

 lition, by exsiccation, by crushing, or by poison. In 

 the latter case it is difficult to ascertain the fact on 

 account of the complications resulting from the 

 presence of the poison. 



d. A question that presents itself is this: Is this reac- 

 lion specijic? In other words: Is it only on living 

 infusoria of their own species that dead bodies have 

 this effect? It is not unlikely a priori that this 

 is so considering what is seen to take place in the 

 processes of fecundation and of conjugation. 

 My very first experiments on this question seemed 

 to favour the theory of specificity, but by further 

 investigation I saw that there is no such exclusive 

 reaction of living infusoria in the presence of dead 

 ones of their own species. But, on the other hand, 

 there is a considerable quantitative difference as to the 

 force with which the different species of infusoria 

 react against dead bodies of one and the same 

 species. 



