366 The Unitij of the Organism 



nuclear participation in the development of organs. John- 

 son's observations on these nuclei were very incomplete, but 

 such as he made are significant. H^ found undoubted evi- 

 dence that some of them divide when the animal divides ; 

 but in no case was he able to follow all the details. The 

 points made out which seem to bear on the main question 

 before us are : "I made out," he says, "65 micronuclei adher- 

 ent to the two [pieces of the macronucleus], but none were 

 found in the spindle stage except the two above-men- 

 tioned." ^ The point of interest for us is that so far as the 

 evidence goes, the dividing micronuclei were closely related 

 spacially to the macronucleus, which is another way of 

 saying that they were 7iot closely related spacially to the 

 developing organs, so that if they played any direct part 

 in this development they did so through some "action at a 

 distance" — a sort of action which, though as we now know 

 may be a real factor in organic development, can be in- 

 voked as an explanation of morphogenesis only with the 

 greatest caution. 



Another point of interest touched by Johnson's observa- 

 tions concerns the time of the division of the micronuclei 

 relative to the division of the macronucleus. When the 

 dividing micronuclei were observed the macronucleus was 

 "at complete condensation and in two distinct pieces." " 

 Turning to the account of the behavior of the macronucleus 

 during division of the animal, we read, "the meganucleus 

 has assumed the spherical shape [state of condensation] 

 when the pharyngeal funnel has begun to form" ; ^ in other 

 words, at a time somewhat earlier than that shown in figure 

 12. That is to say, so far as the observations go, the in- 

 dications are that fission of the animal begins in the cyto- 

 plasmic part of the body not only before the macronucleus 

 undergoes any change, but also before the division of the 

 micronuclei. 



Apparently the behavior of the micronuclei during asex- 



