6o8 



H. S. 'Jenjjings 



In each case the truncation of the anterior end persisted for a 

 few generations (two to five), being transmitted of course to but 

 one individual in each generation. At each fission, as a rule, the 

 peculiarity of the anterior end of this individual became less 

 marked, till it became invisible. There is thus a marked tend- 

 ency at the time of division to regulate the body form, bringing 

 it back to the normal condition. 



c Posterior Part of the Body Truncate or Lacking 



Many individuals were found in which the posterior half of the 

 body seemed almost lacking. The body ended bluntly just 



Fig. 1 1 History of a race derived from an individual in which the posterior part of the body was 

 extremely short and rounded. The posterior end is to the left. The peculiarity was transmitted to one 

 individual in each generation, becoming less and less marked, till in generation 5 it has disappeared. 



behind the mouth. The animals were about half the normal 

 size, and presented much the appearance that would result if they 

 had been cut in two transversely just behind the mouth (Fig. ii). 

 I followed the history often cases of this sort. In all cases the 

 bluntness of the posterior end is transmitted, usually in weak- 

 ened form, to the posterior individual resulting from division, 

 while the anterior individual is quite normal in form. This con- 

 tinues as a rule for three or four generations, the posterior end 

 approaching after each division more nearly the normal form, 

 till finally regulation is complete, and all the progeny have the 

 usual shape. A typical case is shown in Fig. ii. 



