Evidence from Proturwdits 367 



ual fission and devclopiiR'iit in Stentur has not Ijcth iLvxaiii- 

 ined since the publication of Johnson's |)a|Kr, so all the 

 light we have on the ])art played by the uiicronucUi in tlu- 

 ontogeny of these animals is still fragmentary and indinct 

 so far as the particular j)oint now befoi'e us is concenu'd. 

 Muslow ^ presents certain observations on these bodies din- 

 ing conjugation that bear on the ])()int indirectly. I'or one 

 thing, he confirms Johnson's observation tiiat the iiiicio- 

 nuclei are situated typically close around, indeed are adlu r 

 ent to the macronucleus. But perha})s the mo.st 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 })art 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 cliro- 

 midia and on the mitochondria, affect the problem of nuclear 

 participation in organ development. But our general j)osi- 

 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 i)lay in development, so what the 

 nucleus does or does not do concerns us oidy secondarily. 

 This beine- the case, when Johnson savs (and it should 

 be remarked that descriptions of like })ur{)()rt by othei- >tu 

 dents concerning other protozoans, are almost nuniberli'>s ), 

 the "gradual evolution of structures so com])licated as mem- 

 branellae from a mass of indifferent protoplasm." \\v take 

 the description at its face value and hold that no matter 

 what outside influences may operate on this |)roto|)la>m, 

 it itself plays an active and essential part in l)ringing about 

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

 since these results are a number of organic parts idiich 



