PHYSIOLOGICAL DEGENERATION IN OPALINA. 641 



(Schaudinn). lu the first three of these increase in the size 

 of the nucleus has frequently been observed as a preliminary 

 occurrence. In Actinosphgerium giant nuclei are formed 

 Avhen the animal degenerates owing to overfeeding. Break- 

 iug up and discharge of the nucleus usually follows — that is 

 to say^ chromidia play a part in the degenerative phenomena. 

 In TrichospliEerium^ when degeneration is induced by 

 starving the organism, the nuclei clump themselves together 

 at certain points. This agglomeration is not followed by 

 fusion. Stole has observed a similar condition in starved 

 Pelomyxas. And I may here recall the observation of 

 Maupas on Paramoeciunij that the fragments of the old 

 meganucleus sometimes fuse with the new meganucleus of an 

 exconjugant if it be starved. 



In the degenerating sporont of the coccidian Cyclospora 

 the polar bodies divide until eight are formed, and microga- 

 metes then attempt to fertilise each of these. In later stages 

 of degeneration pigment is formed ; and Prandtl has shown 

 that pigment appears in a degenerating Amoeba proteus, 

 and is formed from the chromatin of the nucleus. In this 

 particular form there is also a curious tendency for the 

 nucleus to surround food masses in the cytoplasm. 



Nuclear fusion sometimes takes place — independently of 

 any sexual process — in multinucleate Protozoa during, or 

 following, encystment : e.g. in Dileptus (Prowazek). 



Hyper-regeneration occurs in Stylonychia if mutilated 

 when in a degenerate condition (Prowazek). Loss of ap- 

 pendages has been frequently observed in many different 

 Protozoa undergoing degenerative changes. It is unneces- 

 sary to give a number of examples, but Trichosphserium 

 and Paramoecium may be cited as good instances. 



Chromidia of the type I have described in Opalina (i.e. 

 bladder-like, or blaschenformig) have only been noticed, so 

 far as I am aware, in one other Protozoon, Bodo lacertae, 

 Grrassi. And here they are formed as a preliminary to 

 ga^mete formation and autogamy (Prowazek). 



Very curious in many other ways is the parallel which 



