CONJUGATION IN BLEPHARISMA UNDULANS 677 



of degeneration, which in Biitschh's and my experience follows 

 conjugation, make Stein's interpretation more plausible. 



Biitschli's observations were more complete and more defi- 

 nite than Stein's although the finer details are still unknown in 

 B. lateritia. A free translation of his description of the nuclear 

 changes runs as follows : 



The uniform and finely granular (macro) nucleus as shown by treat- 

 ment with acetic acid, undergoes no changes during the entire process 

 of conjugation, and passes on to the separated animal in its original 

 form. In flattened conjugating animals treated with 1 per cent acetic 

 acid on the other hand, one notices very distinctly, a number of small 

 nucleolus (micro nucleus) -like bodies. These give the impression of 

 small cell nuclei which appear as though enclosed within a dark mem- 

 brane and consist of a dark central or ex-centric granule. Once fine 

 fibers were seen running from this central granule (karyosome) to 

 the membrane, and again one finds these vesicles sometimes without 

 a central granule (karyosome) l)ut composed of fine particles. The num- 

 ber of such bodies found in the cells of conjugating animals varied 

 within rather mde limits, once there were only two, again three, 

 seven, eight, while in one pair the one individual contained eleven the 

 other one six. After conjugation there is no further evidence of these 

 bodies; on the other hand in a specimen that had just finished conju- 

 gation there was one very distinct nucleolus capsule in front and 

 one l)ehind the nucleus (macronucleus). The capsules were beauti- 

 fuU}^ striated \\nt\\ two dark staining bodies in the centers of each 

 fiber, which together formed a double granular zone in the equator 

 of the capsules. 



In place of these two undeniable nucleolus capsules one finds in 

 animals shortly after conjugation two minute pale bodies of oval form 

 on the side of the nucleus. These, after treatment with acetic acid, 

 show large dark granules. They grow rapidly into pale round spheres 

 in which an ex-centric granule is invariably present. In contrast 

 to this development the nucleus (old macronucleus) becomes pro- 

 gressively smaller and denser and shows unmistakable signs of degen- 

 eration. 



On the third day after completed conjugation, animals were found 

 in which there was no trace of a (macro) nucleus and there is no doubt 

 that the degenerated nucleus had been thrown out of the cell. The 

 new light spheres continued to enlarge and appeared to be made up 

 of small granules while the larger bodies had apparently disappeared 

 (1. c, pp. 315-316). 



All of the stages observed by Biitschli I have been able to 

 duplicate in the case of B. undulans, and in addition have been 

 able to trace out the beginnings and to a certain extent the his- 



JOURNAL OF MORPHOLOGV, VOL. 23, NO. 4 



