RESEARCH PROBLEMS IN THE OPALINID^ 235 



of the structure of protoplasm might well include both ectosarc 

 and endosarc of opalinids. 



3) The inclusions in the cytoplasm need much further study. 

 a) In the ectosarc are one, two, or three sorts of these bodies. Are 

 these divergent conditions of the same thing, or are there two or 

 three distinct sorts? Are the large blotches, sometimes giving a 

 yellowish tinge to the living animal when seen in white light, espe- 

 cially reflected Hght, paraglycogen {Cf., Metcalf, 1909), or what 

 are they? Are the "ectosarc spherules" integrally united to the 

 neuro-muscular complex {Cf., Kofoid's as yet unpublished 

 paper) ? Is there any morphological or genetic relation between the 

 spherules of the ectosarc and those of the endosarc? h) What are 

 the endosarc spherules — chemical composition, function, origin? 

 Do they arise from the chromatin of the nucleus (Metcalf, 1909) 

 or by division of themselves (Tonniges and others) ? What is the 

 meaning of their partial or complete (?) disappearance in the 

 gametes? How do they become restored in the growing zygote? 

 The whole subject of protoplasinic inclusions in the ciliata, indeed 

 in PROTOZOA and, for that matter, in protista, greatly needs study, 

 and in any such study the opalinids deserve special attention. 



4) The "silver-line structures" (neuro-motor complex) should 

 be studied by silver nitrate impregnation and exposure to light and 

 also by the methods of Kofoid and his school, this especially in 

 binucleated opalinids, in which the relations are much less compli- 

 cated than in the multinucleated forms upon which Kofoid worked 

 (Kofoid's results were described at the meetings of the Society of 

 Zoologists, in December, 1928. but the paper is not yet published). 

 Incidentally the results should be scrutinized to see if they give 

 indication of the former position of a mouth. 



5) The nucleus: a) Chromatin, metabolic and genetic; the de- 

 struction of the former at the sexual period ; especially its reap- 

 pearance in the growing zygote (not observed by Metcalf) and the 

 source from which it arises and all the attendant circumstances ; 

 the greater care exercised over the division and distribution of the 

 vegetative chromatin in binucleated opalinids than in multi- 

 nucleated genera, and the interpretation of this difference; the 

 circumstances of the ready appearance of abnormalities in the 

 metabolic chromatin bodies ("macrochromosomes") when the ani- 

 mals are placed under unaccustomed conditions ; the influence of 

 different environmental factors (oxygen, pH, different foods, etc.) 



