AXIAL GRADIENT IX CILIATE INFUSORIA. 53 



preted the inability of non-nucleated pieces or cells to regenerate 

 to asphyxiation in the absence of the nucleus. Vervvorn ('91, 

 '04), on the other hand, has shown that non-nucleated pieces of 

 various ciliates are as susceptible to lack of oxygen and recover 

 as readily when it is present as nucleated cells or pieces. These 

 facts indicate that respiration takes place in the cytoplasm, even 

 when the nucleus is absent. Later investigations by various 

 authors support and confirm Verworn's view. 



My own observations show that the nucleus is much less sus- 

 ceptible to cyanide than the cytoplasm. If the cyanides inhibit 

 in some way the oxidation processes as most authorities believe 

 the much greater susceptibility of the cytoplasm indicates that 

 the oxidations are localized in it, at least to a much greater 

 extent than in the nucleus. Moreover, the existence of a gradient 

 in susceptibility to cyanide in the cytoplasm and particularly in 

 the ectoplasm indicates that different rates of oxidation are 

 localized in different regions of the unicellular body in very much 

 the same way as in multicellular forms. But even if the cyanides 

 produce their effect in some other way than by inhibiting the 

 oxidation processes specifically, whether their action is upon 

 some other reactions of the metabolic complex or upon the meta- 

 bolic substratum of the cell, they make it evident that a dynamic 

 gradient exists along the main axis of the unicellular ciliate 

 infusorian body. 



SUMMARY. 



1. An axial gradient in susceptibility to KCN is present in 

 Stentor, Stylonychia, Vorticella, Carchesium and Paramoscium. 

 This suceptibility gradient indicates the existence of a gradient 

 in rate of metabolism or of oxidation processes. 



2. In all forms examined the anterior or apical region is the 

 highest point in the general gradient, although localized regions 

 of still higher rate such as the vacuolar regions of Paramoscium 

 may exist. 



3. A close parallelism exists between the character of the 

 gradient and the morphological and physiological features of 

 the species. Where the gradient is uniform and slight, structural 

 and physiological differences along the axis are slight and where 



