CHILOMONAS PARAMCECIUM EHRENBERG. 21 7 



of a membrane, the aggregate resembles the nucleus of Euglena. 

 Division takes place as in Euglena, the intranuclear division- 

 center dividing first. After division the chromatin granules 

 again disperse and the division-center becomes again cytoplas- 

 mic (Fig. 143)." "An intermediate stage between this condi- 

 tion and the condition in Euglena is shown by some species of 

 Chilomonas and Trachelomonas in which there is no nuclear 

 membrane, but in which the chromatin remains permanently 

 aggregated about the division-center." Kellicott ('13), in his 

 statement "a definite nuclear membrane may be absent at first, 

 as in Chilomonas," seems to follow Calkins's earlier conception 

 that these granules represent a nucleus without a nuclear mem- 

 brane. 



It is interesting to see that Calkins ('08) modifies his view- 

 point somewhat. He no longer considers these granules as 

 representing a nucleus, but implies that they are nuclear in 

 origin. Though it is not exactly clear that he has changed his 

 opinion about these chromatin granules such is strongly implied 

 when he says "there is probably no great difference between the 

 above-described method of idiochromidia formation by trans- 

 fusion, whereby the chromatin materials percolate through the 

 nuclear membrane in fluid form, and that by nuclear dissolution, 

 whereby the peripheral portion of the nucleus becomes scattered 

 in granular form throughout the cell body" and then in his 

 legend to Fig. 49 on the same page prints " Chilomonas para- 

 mcecitim to show the alveolar structure of protoplasm prior to 

 idiochromidia formation." This idiochromidia he at this place 

 considers to be the "sexual or racial chromatin" of the cell as 

 contrasted with chromidia which is "functionless extranuclear 

 chromatin." 



By the implication of his later words he has given up the 

 idea that the nuclear-like body at the base of the pharynx is 

 a nucleus. He now sees, in what he had taken to be the chro- 

 matin granules of a distributed nucleus, grains of idiochromidia. 

 These, he says, are of nuclear origin. He further thinks that 

 these chromatic granules play an important part in reproduction. 



Our own observations indicate that there is a definite or 

 clearly defined nucleus in Chilomonas paramcecinm. This 



