Notes on a New Boveria species. 1 ' 



(fig. 17). Now in this upper individual the micronucleus divides 

 into two, and then follows the binary fission of the body, whereby 

 each of the two resulting individuals receives both one micronucleus 

 and one moganucleus. The result is, tliat the three individuals 

 arising from the trinal fission of an ex-conjugant contain each a 

 mcganucleus and a micronucleus. Thus they have now returned 

 to the condition of the resting stage. 



Stevens has fully described the ordinary binary fission in 

 Boder.ia siihcylindrica. In that Ccàsc, it is said that the granular 

 part ef the meganuclear plasm divides into three masses, two polar 

 and one central ; the central one again divides into two, each of 

 which fuses with one of the polar, so that, ultimately-, there exist 

 pnly two granular masses representing the meganuclei of the two 

 individuals that shall arise from the fission. In Boveria labialis, 

 we have never come across .a case of the division of the ex- 

 conjugant meganucleus taking place in a similar way. The 

 ordinary binary fission in the present species proceeds in the 

 following way. In full-grown individuals ready to" multiply, the 

 micronucleus divides in the manner already described, essentially 

 agreeing with Stevens' description. At the time when the long 

 drawn out micrönüclear spindle approaches the likewise elongated 

 meganucleus, the granular contents of the latter are found in the 

 contracted state, the chromatin granules being found scattered on 

 the surface of the large mass consisting of the plasmosomic gra- 

 nules. About this time the organism loses its cytostome as well 

 as the oral ciliuy spire. When the micronuclear division is 

 finished, the two daughter micronuclei enter into the resting stage 

 and come to be situated nearly at opposite poles of the mega- 

 nucleus. Meanwhile, the first sign of the fission makes its ap- 

 pearance as light and incomplete ring-furrow running obliquely 

 around the middle of the body. Before the fission is completed, 



