680 GARY N. CALKINS 



In the meantime the old, encapsulated macronucleus under- 

 goes fragmentation, the process showing no time relations in 

 i-egard to the changes of the micronuclei (figs. 13 to 23). Sooner 

 or later the fragments show a well-marked granular degenera- 

 tion (fig. 14) and ultimately disappear, probably by absorption 

 in the protoplasm. 



The four daughter nuclei formed by the second division of 

 the fertilization nucleus next show characteristic changes lead- 

 ing to the formation of the new macronuclei. They appear as 

 deeply staining granules surrounded by a more feebly staining 

 homogeneous matrix. The latter increases remarkably in bulk, 

 probably by elimination of chromatin material from the micro- 

 nucleus, until it attains the size of the macronucleus in vegeta- 

 tive cells (figs 24 and 25). These are the 'pale round spheres' 

 which Biitschli described in 1876. In them, either central or 

 ex-centric, are the micronuclei which are occasionally found 

 in the process of division (figs. 24 and 25). These 'pale round 

 spheres' are the new macronuclei. The further history of the 

 nuclei of the ex-conjugants is unknown. The organisms rapidly 

 grow smaller and ultimately die without division. 



DISCUSSION 



The structures ar.d activities of Blepharisma undulans bring 

 up again some large questions in protozoology. Of these, two 

 in particular demand further consideration, viz., the origin 

 and significance of macro- and micronuclei, and the effects of 

 conjugation. 



There is a strong probability that B. undulans and B. lateritia 

 are one species, since the nuclear and peristomeal structures 

 of undulans are so variable. In both types the micronuclei 

 have hitlierto been overlooked in the vegetative stages. Ble- 

 pharisma clarissima Anigst., on the other hand, appears to be a 

 distinct species with a characteristic beaded macronucleus 

 and numerous micronuclei visible in the vegetative stages. 

 The contractile vacuole, also, with its feeding canal is a specific 

 characteristic. 



