NOTES AND LITERATURE 



PROTOZOA 



Doflein's "Lehrbuch der Protozoenkunde." 1 — No group of ani- 

 mals affords a more direct approach to the problems of evolu- 

 tion than the Protozoa and few offer such varied data for their 

 discussion. The organism and the individual are here reduced 

 to lowest terms and the processes of growth, differentiation, 

 degeneration, regeneration and reproduction in the most varied 

 forms are found in astonishing variety and complexity. The 

 phenomena of overcrowding, rapid destruction, parasites and 

 parasitism, immunity, variation, speciation, isolation and per- 

 haps even mutation, with all of their consequences on structure 

 and reproduction, are illustrated in varying degrees of diversity 

 and completeness. It is therefore to be expected that a thor- 

 oughgoing review of the rapidly augmented literature of proto- 

 zoology by Professor Doflein will yield some new points of view 

 or at least a new perspective in which old conclusions and 

 hypotheses may be tested. 



The biogenetic law. for example, in the opinion of the author 

 of the "Lehrbuch" is very doubtfully applicable to the Protozoa. 

 External factors profoundly affect the form and structure of 

 these simple organisms. Increased alkalinity of the water 

 changes Amaba Umax to .1. radiosa, as Verworn has shown. 

 Trypanosomes varv greatly in appearance and virulence, accord- 

 ing to the hosts in which they are cultivated, and in culture 

 media locomotor organs are lost and nucleus and blepharoplast 

 are shifted into new relations in the cytoplasm. Reproductive 

 processes are profoundly modified by temperature and chemical 

 media. The kind of food, according to Faure-Fremiet, affects 

 the structure of VoriiceUa. The form changes, therefore, 

 through which a protozoan runs in its life cycle are to be re- 

 garded as moulded by external influence rather than by internal 

 factors of heredity and the production of similar structures is a 

 phenomenon of convergence rather than a proof of relationship 

 or descent. 



This point of view determines Doflein's treatment of certain 



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