CONJUGATION OF VORTICELLA 213 



The combination nucleus soon elongates to form a fibrous 

 spindle, and divides by mitosis. Two more divisions follow, so 

 that the macrogamete contains eight similar nuclear corpuscles. 

 One of these does not grow any further, but assumes the char- 

 acters of a micronucleus. The other seven become spherical, 

 and grow rapidly till each consists of a central mass of granular 

 matter separated by a clear space from a well-defined nuclear 



Fig. 46. 



Diagram of the course of conjugation in Vorticella monilata, constructed on the 

 same principle as fig. 43, which should be compared. (After Maupas.) 



membrane. The fertilised macrogamete, if well fed, is now 

 ready to divide. The large corpuscles, which may now be 

 called macronuclei, do not divide, but are distributed to the 

 offspring, four passing into one and three into the other of the 

 two individuals ' resulting from the first division. The micro- 

 nucleus, on the contrary, divides, one of its products passing 

 into each of the daughter Vorticellae. The rest of the process 

 has not been determined with absolute certainty, but it is 



