258 BULLETIX 120, UNITED STATES NATIONAL MUSEUM. 



plete and completely functional nucleus, containing both trophic 

 and reproductive chromatin in full activity. In the Euciliata one 

 of the two nuclei has become specially developed for metabolic 

 activitj'', being greatly hypertrophied. The other nucleus remains 

 small and for the most part inactive during the vegetative phases 

 of the life cycle. When conjugation occurs only the micronucleus 

 takes part in the sexual process, the hypertrophied metabolic mega- 

 nucleus being absorbed. Functionally there seems a parallel between 

 the macrochromatin of Opalinidae and the macronucleus of Euciliata, 

 and similarly between the microchromatin and the micronucleus in 

 the two groups. In both groups the hypertrophied metabolic chro.- 

 matin is absorbed into the cytoplasm when the sexual process occurs, 

 and only the idiochromatin shares in this process. 



Among the lower Protozoa the Plasmodroma, somewhat similar 

 conditions have been described, but there is need of more detailed 

 study before comparisons can confidently be made. 



Schaudinn and others have regarded the formation of chromidia 

 in Plasmodroma as the process by which vegetative and reproductive 

 chromatin are separated, and this may well be true. But if so, how 

 shall we regard the processes of chromidia formation in Opalinidae, 

 as described by Neresheimer? In my former studies of Opalinidae 

 I observed degeneration of the nuclei in a few individuals of Opaiina 

 obtrlgona and perhaps in one specimen of Protoopalina caudata^ but 

 I regarded the phenomena as probably abnormal. All the phe- 

 nomena are so much easier to follow in the binucleated genera that 

 they should be studied in detail in Protoopalina^ or preferably in 

 Zelleriella, and it is my intention to collect material for this study. 

 In my present material there are three infections of Zelleriella which 

 may possibly indicate that in this genus the old nuclei degenerate 

 and new^ nuclei are formed in the cytoplasm, much as Neresheimer 

 has described for Opaiina ranaimin^ but it seems more probable the 

 phenomena are abnormal, perhaps associated with parasites within 

 the Opalinids. Of these three infections in my material, one is in 

 Zelleriella [of Bufo woodhousi], two others are in Zelleriella hirsuta 

 from Bufo cognatus. The material is not well enough preserved for 

 satisfactory study of minute detail and, as I hope to get better ma- 

 terial, it is not worth while to discuss at any length the phenomena 

 observed. We may note one fact, that in Z. [of Bufo tvoodhousi] are 

 found some degenerating nuclei which quite closely resemble the 

 degenerating nuclei of Opaiina ohtrigona which I described in 1909. 

 Raff describes certain " abnormal " individuals of an undetermined 

 species of Zelleriella (?), from Livmodynastes dorsalis, in which are 

 seen from two to eight nuclei. It seems likely that these are similar 

 CO the numerous small nuclei in my infections of Z. hirsuta and Z. 

 [of Bufo u^oodhousi]. 



