334 c - M - CHILD. 



indicate that under certain conditions this is not the case. In 

 view of the apparent disagreement between her results and my 

 own further experiment seemed desirable and during the autumn 

 of 1907 and the summer of 1910 I took the opportunity to 

 examine several species of Leptoplanida* which occur at La Jolla r 

 Calif., with reference to this point. In 1905 I had worked with 

 L. littoralis at Pacific Grove and obtained results similar to those 

 described for L. tremellaris. 



My conclusions from this later work are essentially the same 

 as those reached in my earlier paper. Removal of the ganglia 

 with as little of the surrounding tissue as possible always results 

 in decreased rapidity and completeness of regeneration, w r hatever 

 the method of operation employed. In many cases, however, 

 groups of eye spots appear in the new tissue, even when the 

 ganglia are wholly absent, and in such cases the regeneration is 

 always more rapid and more nearly complete than when the 

 eye spots do not appear. 



When the ganglia are removed by a cut from one side of the 

 head, as in some of . Morgan's experiments, more new tissue is 

 often formed, or it forms more rapidly, in the deep cleft made by 

 the cuts than on a nearly flat terminal surface. This, however, 

 is not due to any specific effect of the anterior tissue, but is merely 

 a very general characteristic of wound-healing, not only in Tur- 

 beUaria, but in many other forms, and is doubtless due to the 

 fact that nutritive and other conditions for growth are better in 

 such a cleft, where the growing parts are in contact on both sides 

 with other tissue, than on surfaces where such contact exists 

 only on one side. 



I believe that the important point in connection with the 

 problem of the influence of the central nervous system on re- 

 generation in these forms lies in the question as to what con- 

 stitutes the central nervous system. As Morgan states, thecepha- 

 lic ganglia in the polyclads are enclosed in a definite sheath, but 

 a further point of great importance which she does not consider 

 at all is that the nerve roots contain numerous ganglion cells 

 for a considerable diMauee from their point of origin in the ganglia. 

 Reference to Lang's monograph of the polyclads 1 is sufficient to 



'Lang. "Die Poly I;I.|I-M >\<-~- Golfes \<>n Nr.iprl." Fnumi nn<l Flora des Colfes 

 von Neapel, XL, Leipzig, 1884. 



