336 C. M. CHILD. 



Since my later experiments confirm in all respects my earlier 

 work, it seems unnecessary to describe them in detail and to 

 figure all the various methods of operation and the results. I 

 can only conclude that the apparent absence of effect of gan- 

 glionic removal upon regeneration in certain cases is due to one 

 of two things, viz., failure to remove the ganglia completely, or 

 the presence of the intact nerve roots. Morgan's experiments 

 do not in any way prove that the central nervous system does 

 not exert an influence upon the rapidity and amount, and so 

 far as the sense organs are concerned, upon the character of 

 regeneration in the polyclads. 



As regards one point, however, Morgan's results as stated in 

 her paper disagree so completely with my own that some further 

 consideration is necessary. In the concluding paragraph of her 

 paper the statement appears that "regeneration of the anterior 

 tip of the worm, that is when the worm has been cut off anterior 

 to the ganglia, occurs in the absence of the ganglia as well as 

 when they are present." Individuals with the ganglia removed 

 and the end cut off anterior to the ganglionic region regenerated 

 as rapidly and completely as controls with uninjured ganglia 

 and the anterior end cut oft" at the same level. In these experi- 

 ments the ganglia were removed by using the cut end of a straw 

 as a punch and after the wound thus made had healed the anterior 

 region of the head was cut off. 



I have performed this experiment a large number of times and 

 on various species of Leptoplanidae and with essentially uniform 

 results, viz., that in all cases where the ganglia were actually 

 completely removed, regeneration \\.is less rapid and less complete 

 than in control experiments with uninjured ganglia. Moreover 

 the larger the portion of the nerve roots removed in addition to 

 the ganglia themselves, the less rapid and less complete the re- 

 generation. The operation is by no means easy to perform suc- 

 cessfully and in many cases larger or smaller portions of the 

 ganglia remain: such cases show all gradations from complete 

 regeneration to a condition essentially like the pieces from which 

 the ganglia are totally absent, but they must of course be regarded 

 as unsuccessful experiments for our present purpose. 



In my experiments the ganglia \\ere removed with a straw in 



