THE OPALINID CILIATE INFUSORIANS. 



23 



tained seem to indicate the total expulsion of the massive chromo- 

 somes, leaving behind in the nucleus finally only eight small oval or 

 spheroidal chromosomes of about the size se6n in the gametes. At 

 the time all these phenomena were observed, I did not have in mind 

 the distinction between massive and granular chromosomes, and 

 there is therefore need of restudy of these stages. The observations 

 made are consistent with and would point to the conclusion that 

 the massive chromosomes are all bodily extruded before the forma- 

 tion and the union of the gametes, but the conditions have not been 

 carefully scrutinized with reference to this question, and it must 



Fig. 10. — Pkotoopalina intestinalis ; a, h, and c are serial sections of one individ- 

 ual ; d IS ONE FROM A SIMILAR SERIES OF ANOTHER INDIVIDUAL. BOTH ANIMALS ARE 

 discharging from their nuclei GREAT AMOUNTS OF CHROMATIN. X 500 DIAMETERS. 



(After Metcalf, 1909.) 



therefore be regarded as still needing further study. If the 

 massive chromosomes are wholly extruded, as seems to be the case, 

 they must apparently be regarded as vegetative in function, like 

 the meganucleus of Euciliates, in contrast to the reproductive gran- 

 ular chromosomes. If the macrochromosomes are not wholly ex- 

 truded but are merely greatly reduced in bulk by extrusion of 

 most of their substance, the comparison with the conditions in the 

 Euciliates is even more interesting. What, then, is the meaning of 

 the degeneration of nuclei, which has been seen at an earlier stage 

 of the life-history in Cepedea^ Opalina^ and Zclleriella^ if indeed 

 these phenomena be not pathological ? What is the relation between 

 these two sets of phenomena ? The presexual and the sexual phases 



