TOWARD A GENETICS OF STENTOR 325 



in these two species in the diagrams and legends of Fig. 93 and 94 

 and therefore will touch only the main points in the following 

 paragraphs. 



S. coeruleus: The size of conjugating animals is always smaller 

 than the maximum, as Hamburger had also noted, and Johnson 

 observed that conjugants were without food vacuoles apparently 

 from the start. Sometimes the partners are of different sizes but 

 they are not necessarily so and hence there was no indication of 

 ** gamete" differentiation. All this accords with my own observa- 

 tion. Attachment is by the anterior rim so that the partners rest at 

 an angle to one another and swim together with their axes parallel. 

 In the conjugants I have observed there was always a special place 

 of attachment : a patch immediately below the membranellar band 

 and to the left of the mouth. In location this point corresponds to 

 Hamburger's figure though she said that attachment was by the 

 membranellar bands. That this locus of joining is not invariable, 

 however, is shown by the fact that Mulsow often found three 

 animals together in conjugation, all undergoing nuclear changes 

 simultaneously. He also found that the degree of union is variable, 

 from a small bridge to quite complete fusion of the two lateral 

 surfaces, and that this does not depend on the stage of conjugation. 

 Hence there may be endoplasmic fusion, but the migratory nucleus 

 always penetrates through a separating, pigmented membrane 

 toward the anterior end. The duration of the union is about 

 30 hours, which is not unusual, and nuclear renewal is not 

 completed until 10 days after separation. 



The old rnacronucleus first breaks up into separate nodes which 

 then lose their orderly arrangement in a chain as well as their 

 adherence to the inside of the ectoplasm. Johnson had observed 

 that the nodes carry cytoplasmic (attachment?) threads as they 

 break loose from their former locations and are carried about in 

 the cell by a cyclosis of the endoplasm, which is unusually rapid 

 in conjugation. At this time. Hamburger said that the nodes lose 

 their amorphous character and show a honeycomb structure. The 

 original macronucleus so remains until its parts begin disappearing 

 as soon as the new macronuclear anlagen have attained considerable 

 size. 



After breakup of the macronucleus into separate nodes, the 



