NUCLEI AND KINETIC ELEMENTS 93 



generally regarded as a stage in the life history of an entirely differ- 

 ent parasite of the little owl (Minchin enumerates no less than five 

 different types of protozoon parasites which may live simultaneously 

 in the blood of this owl). A second contested point is the origin 

 of the kinetic elements of the cytoplasm by mitosis. Other con- 

 tested points and untenable conclusions drawn from them have to 

 do with sex differentiation and parthenogenesis which need not be 

 considered here. 



It is not at all impossible that Schaudinn may have seen the emer- 

 gence of a kinetic element from the endosome of the nucleus as 

 described above in the case of Ndgleria gruberi, and the similar 

 emergence of a basal granule or blepharoplast from a chromatoid 

 mass in the cytoplasm. The interpretation of such possible stages 

 as mitotic nuclear division, and the smaller products of such division 

 as nuclei, has led to numerous theoretical developments which have 

 only a narrow basis of fact. Tw^o years after Schaudinn's paper 

 appeared, Woodcock translated it into English and conferred the 

 name "kinetonucleus" on the smaller body resulting from the 

 heteropolar mitotic division, and the name "trophonucleus" on the 

 nucleus of the cell. Schaudinn himself was the first to announce 

 this binucleate character of the trypanosome body and the hypoth- 

 esis was taken up by his followers, Prowazek, and notably Hartmann 

 (1907). The latter developed the conception into an elaborate 

 view of original nuclear dualism upon the basis of which he created 

 a special group of the Protozoa including trypanosome-like flagel- 

 lates and hsemosporidia, which he called the "Binucleata."* As 

 Doflein points out, not only do the ha^mosporidia have no blepharo- 

 plasts as do the trypanosomes, but blepharoplasts in the latter are 

 not to be considered nuclei. In this use of the term blepharoplast 

 Doflein includes the structure to which Woodcock gave the name 

 kinetonucleus, but he employs the term in a special sense as a 

 kinetic element, while German writers generally use it for structures 

 of widely different significance. Thus Schaudinn, although con- 

 vinced of its nuclear character, nevertheless called it a blepharo- 

 plast. French writers as a rule speak of it as a centrosome {e. g., 

 Mesnil, Laveran, etc.) as do some English observers (e. g., Moore 

 and Breinl) ; many of the latter, however, follow the original nuclear 

 interpretation, Bradford and Plimmer following Stassano, regarding 

 it as a "micronucleus" and comparing it with the smaller nucleus 

 of the ciliates, while Woodcock and Minchin considered it a "true 

 nucleus." 



The essence of the problem indicated by the various usages of 

 these familiar terms comes down to a decision as to whether the 

 so-called kinetonucleus, by which is meant the relatively large 



* For critiques of the Binucleata, see particularly Minchin (1912), Dobel 

 (1911.) 



