6i8 H. S. Jennings 



progeny; no tendency for the mutilation to be duplicated in new 

 individuals. There is no tendency to produce a race of mutilated 

 individuals, any more than there is in Metazoa. Regulation takes 

 place at the time of fission, so that after several fissions the normal 

 condition is restored. 



^ Acquired Characters That Tend to be Inherited 



g Acquirement and Inheritance of a Tendency for the Adults to 

 Remain United in Chains 



The acquired characteristics thus far described have shov^n no 

 tendency to be inherited in such a way as to produce a race bearing 

 the new character in question. We now come to a case in which 

 such a tendency actually showed itself. The difference between 

 this case and the others is instructive, suggesting what must be the 

 essential nature of an acquired character that may be inherited. 



The characteristic in question is a tendency for the adult indi- 

 viduals to remain united in chains. This tendency appeared in 

 the line a, which we have already described in connection with 

 the transmission of a long spine (pp. 589-604); the beginnings of 

 the characteristic now under consideration have been set forth in 

 that description. In the process of growth the broad base of the 

 long spine (Fig. 4, ^) became drawn out, till in the individual 

 ^1.2.1.2.1.2.1.2 j^ formed a ridge running along the aboral surface 

 nearly the entire length of the body (Fig. 4, ^). At the next fission 

 it was found that the fission plane did not pass so readily through 

 this ridge as through the remainder of the body, so that the two 

 resulting individuals did not separate, but remained connected 

 by a bridge passing from the aboral surface of one to that of the 

 other (Fig. 4, ^°). 



The continued union of the two individuals after fission reap- 

 peared in succeeding generations, both in the individuals formed 

 from the region anterior to the spine (as in Fig. 4, ^°), and in those 

 formed from the region posterior to the spine (Fig. 4, ^^' ^^). In 

 the eighteenth and twenty-first generations three individuals 

 formed a chain (Fig. 20, a). In succeeding generations many 

 such connected individuals and chains were formed. In the fif- 



