498 JOHNSON. [Vol. VIII. 



What purpose is subserved by the multiplication of mega- 

 nuclei in the infusorian body } It seems to me that it is best 

 referred to the same cause as that productive of branched, 

 moniliform, and vermiform nuclei, both among Protozoa and 

 Metazoa. I have elsewhere ('92, p. 138) expressed the view, 

 in agreement with Chun, that one of the prime motives for 

 amitotic division is the distribution of nuclear material through 

 the cytoplasm, and the occasion is especially urgent where the 

 mass of the nucleus (as is the case with Stentor) is small in 

 comparison with the mass of the cytoplasm. A point of inter- 

 est in this connection is the very frequent contemporaneity of 

 meganuclear division when there are two or more meganuclei 

 (Fig. 24). It is the usual thing to find both nuclei at nearly 

 the same stage of division, but not infrequently one will be 

 found to have outstripped the other, so that specimens occur 

 with two separate nuclei and a third constricted one. This 

 indicates a response on the part of both nuclei to the needs of 

 the cytoplasm. 1 



Micro7mclei. — The micronuclei of the Stentors have been 

 among the most difficult to demonstrate of all the Ciliata. 

 They escaped the scrutiny of all the earlier micrographers, and 

 were first seen by Balbiani ('61) at time of conjugation, when 

 they become greatly enlarged. But at that period Balbiani 

 was no more successful than his predecessors in discovering 

 them in the resting condition. A clear account of the pres- 

 ence of micronuclei in the quiescent state was first given by 

 Maupas ('83, p. 661). More recently, Gruber ('86) has con- 

 firmed Maupas' announcement of their presence in 5. ccenileus. 

 Plate ('86), on the contrary, maintains that the minute bodies 

 in question are " Assimilationsprodukte," basing his opinion 

 on the fact that the " granules " are not visible in all speci- 

 mens. As I have succeeded in finding them in mitotic di- 

 vision there is no longer reason for doubting their micronuclear 

 nature. 



The micronuclei of Stentor are difficult to find, not so much 

 on account of their minuteness, as by reason of the vastly 



1 An interesting case of synchronous constriction of a large number of mega- 

 nuclei is given by Gruber {'84b) for Spirostomum lanceolatum, n. s. 



