242 COMPARATIVE ANATOMY 



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 

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



52. 



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

 same principle as fig. 49, which should be compared. (After Maupas. ) 



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

 called meganuclei, 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 Vorticellse. The rest of the process 

 has not been determined with absolute certainty, but it is 

 probable that it follows the course indicated in the diagram, 

 fig. 52. The young Vorticellid with four meganuclei under- 



