THE GENERAL PHYSIOLOGY OF THE PROTOZOA 209 



(Popoff, 184) ; they may also be induced artificially in various 

 ways by unfavourable conditions, such as overfeeding or starvation, 

 changes of temperature, or treatment with reagents (compare 

 Smith, 207 ; Popoff, 186 ; Boissevain, 151). 



A state of depression may be regulated naturally by conjuga- 

 tion, or by restoration of the nucleo-cytoplasmic balance through 

 a process of self-regulation on the part of the organism. The 

 regulative processes consist of absorption of a large part of the 

 superfluous chromatin, so as to restore the normal quantitative 

 relation of the nucleus and cytoplasm. On the other hand, the 

 depression may lead to complete degeneration of the organism 

 without possibility of recovery, and death ensues by a process of 

 disruption of the protoplasm into granules so-called " granular 

 disruption " (korniger Zerfall). Some examples are given below : 



Actinosphcerium can be brought into a condition of depression either by 

 starvation or overfeeding (Hertwig, 164). In the depressed state a great 

 quantity of chromatin is extruded from the nuclei in the form of chromidia 

 which degenerate into pigment, so that the animal during a depression-period 

 has a characteristic brownish tint, more or less pronounced in proportion 

 to the degree of depression. In extreme cases the protoplasm is bereft of its 

 nuclei, and becomes incapable of continuing to live. The nuclei may become 

 entirely resolved into chromidia ; or some of the nuclei grow to a relatively 

 gigantic size and are cast out, while other nuclei break up ; or the entire 

 medullary layer surrounding the enlarged nuclei may be thrown off. The 

 pseudopodia may disappear altogether or become deformed in various ways, 

 the difference between cortical and medullary substance may be annulled 

 or abnormally increased, and the metabolism may be modified, all these 

 changes being in relation to nuclear alterations. 



In Opalina, according to Dobell (155), physiological degeneration can be 

 induced by starvation of its host, the frog. The degenerating Opalines lose 

 their cilia and become irregular in form j peculiar refringent eosinophile 

 globules appear in the cytoplasm ; the nuclei undergo increase in size and 

 modification in structure, give off chromatin, and undergo irregular fusions ; 

 and the body divides irregularly, sometimes producing buds which contain 

 no nucleus. Ultimately the Opalines disintegrate. 



Prandtl (187) has described the degeneration of Amoeba proteus. The 

 nucleus increases in size and becomes hyperchromatinic. Chromidia are 

 extruded into the cytoplasm, and may there degenerate, with formation of 

 numerous small crystals. The chromatin in the nucleus also degenerates 

 to form a mass of brown pigment, which is extruded en bloc into the cyto- 

 plasm, or forms a ring of fine granules round the nucleus. The pigment may 

 also spread through the whole cytoplasm, giving it a brownish tinge. Finally 

 the nucleus breaks up and disappears altogether. Degenerating amoebae are 

 subject to the attacks of parasites. A noteworthy feature is the tendency 

 of the degenerating amoebae to associate in clumps, and plastogamic fusion of 

 two amoebae was observed by Prandtl. The tendency to fusion may be 

 compared with the agglomeration of trypanosomes, etc. (p. 128), which is 

 common also in degenerating forms or under unfavourable conditions.* It 

 is not improbable that many of the plastogamic unions of Sarcodina often 



* The " conjugations " observed by Putter (201, p. 582) in Opalines kept 

 without oxgyen must have been also phenomena of the nature of agglomeration, 

 since in Opalina syngamy takes places between special gametes, and not in the 

 form of conjugation of adult forms as in other Giliata (p. 453). 



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