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THE AMERICAN NATURALIST [Vol. XLII 



THE PROTOZOA 



Some Recent Protozoa Literature.— Waves of special enthusiasm 

 sweep over the domain of biology as of other sciences; each 

 leaves its mark, passes on and is followed by others. At one 

 time it was the ''section cutlers*' at another the "finder bowl 

 brigade," at present it is genetics. Some investigators are 

 independent enough to swim in quieter waters while some are 

 so bold as to try to make an independent high-water mark long 

 after the wave has passed. To the later group Ilartmann and 

 Prowazek must be assigned, for in a recent paper 1 they deal 

 with the homologies of the centrosome, a problem which has 

 never been solved and one that can not be regarded as obsolete, 

 but which is no longer on the wave of biological enthusiasm. 



Nor is the point of approach at all novel. They see in the 

 nucleus and centrosome of the higher cell types only the remi- 

 niscence of a dual condition in protozoa. To be sure, they bring 

 to bear a great fund of recently published observations, more 

 particularly on protozoan cell structures, and they see in the 

 metazoan nucleus and centrosome the outcome of dimorphic nu- 

 clei in these primitive animals. The two nuclei of the hypothet- 

 ical ancestral form are not of the type suggested by Schaudinn in 

 the early advocacy of this same theory ( Amaba binucleata) , but 

 of the type seen in Trypanosoma, where trophonucleus and 

 kinetonucleus are persistent morphological elements of the cell. 

 They believe that the same dual arrangement is present in other 

 protozoa ; in some the kinetonucleus is reduced to a mere granule 

 outside of the normal cell nucleus (as in the Centralkorn of the 

 Heliozoa) : in others the two nuclei are united to form an "am- 

 phinueleus."' the one encased within the other as in the typical 

 centronuclens. Here is the only really novel point in their 

 discussion, and this can not be accepted, for to assign to the 

 division center in a nucleus of the Huulena type the role of 

 an independent nucleus is a reductio ad absurdum. The authors 



