392 



THE INFUSORIA 



nucleus is formed, namely, the one in the female individual. The 

 male shrivels and dies. The cleavage nucleus divides twice, and 



FIG. 43. 



Two stages in the conjugation of 

 Vorticella monilata. In A the 

 micronucleus of the female lias 

 given rise to four nuclei, the 

 micronucleus of the male to eight 

 nuclei ; the meganuclei (M) in both 

 have disintegrated. In B, which 

 represents a later stage, the 

 cleavage nucleus has been formed 

 in the female ; in the male the 

 migratory and stationary sexual 

 are close together, but do not fuse. 

 (Diagrammatic drawings after 

 Maupas. The ciliated discs are 

 actually retracted during these 

 stages.) 



three of the nuclei enlarge and subsequently fuse to form the new 

 meganucleus, whilst the remaining one forms the new micronucleus. 



REGENERATION. Several 

 series of experiments have now 

 been recorded which prove that 

 the Ciliata possess very con- 

 siderable powers of the re- 

 generation of lost parts. If, 

 for example, a Stentor be cut 

 into two parts transversely, 

 the upper part will, in a little 

 while, close up the wound, and 

 eventually form a base similar 

 in all essential respects to the 

 parts that are lost ; the lower 

 portion will, on the other hand, 

 produce a new spiral disc and 

 a new mouth. Thus, as a result 

 of this artificial section of a single individual, 

 two complete individuals are produced. 

 Similarly, sections of the body into three, 

 four, or five pieces may be made, which re- 

 generate and give rise to new and complete 

 individuals. There are limits, however, to 



FIG. 44. 



Stentor coeruleus, Ehrb. M, the long moniliform mega- 

 nucleus ; c.v, the contractile vacuole. If the animal is cut 

 through in the plane a-b, both portions will survive and 

 regenerate lost parts ; if it be cut in the plane c-d, only the 

 lower part containing the meganucleus will survive. (The 

 figure of the Stentor after Saville Kent.) 



this power of regeneration. If a section be made through a 

 Stentor in the plane of the line c-d in Fig. 44, it will be found 



