Evidence from Protozoans 367 



ual fission and development in Stentor has not been reexam- 

 ined since the pubHcation of Johnson's paper, so all the 

 Ijf^-ht we have on the part played by the micronuclei in the 

 ontogeny of these animals is still fragmentary and indirect 

 so far as the particular point now before us is concerned. 

 Muslow ^ presents certain observations on these bodies dur- 

 ing conjugation that bear on tlie point indirectly. For one 

 thing, he confirms Johnson's observation tliat the micro- 

 nuclei are situated typically close around, indeed are adher- 

 ent to the macronucleus. But perhaps the most significant 

 point for us brought out by Muslow's studies is the indica- 

 tion which he finds that the wandering micronuclei, that is, 

 those that pass from one animal into the other during con- 

 jugation, are carried passively, in part at least, by the 

 cytoplasm of the animal. 



In a later section we shall consider the question of how 

 the recent studies on the migration of chromatin granules 

 from the nucleus into the cytoplasm, and also on the chro- 

 midia and on the mitochondria, affect the problem of nuclear 

 participation in organ development. But our general posi- 

 tion relative to this whole matter may be stated here as 

 touching specifically the organogenesis of Stentor. In this 

 section we are trying primarily to find what role the extra- 

 nuclear parts of the cell play in development, so what the 

 nucleus does or does not do concerns us only secondarily. 

 This being the case, when Johnson says (and it should 

 be remarked that descriptions of like purport by other stu- 

 dents concerning other protozoans, are almost numberless), 

 the "gradual evolution of structures so complicated as mem- 

 branellae from a mass of indifferent protoplasm," we take 

 the description at its face value and hold that no matter 

 what outside influences may operate on this protoplasm, 

 it itself plays an active and essential part in bringing about 

 the results. And from this we further hold it to follow that 

 since these results are a number of organic parts which 



