REGENERATION IN POLYCHCERUS CAUDATUS. 



N. M. STEVENS AND A. M. BORING. 



PART I. OBSERVATIONS ON LIVING MATERIAL. 



BY 



N. M. STEVENS. 

 With 21 Figures. 



While enjoying the hospitahty of the Hopkins Seaside Labora- 

 tory at Pacific Grove, Cal., the past summer, I made a few experi- 

 ments to test the powers of regeneration of the red acoelous flat- 

 worm, Polychoerus caudatus, which abounds there in shallow 

 tide-pools on the underside of stones and shells and on Ulva. 

 The object of the experiments w^as a comparison of the regenera- 

 tion of this form which has no definitely diff"erentiated organs — 

 eyes, central nervous system, pharynx, etc. — with the more highly 

 organized fresh-water Planarians, as well as with the results of 

 Schultz ('02) and Child ('04) on Leptoplana and other marine 

 forms which show very incomplete anterior regeneration. 



Method. 



In most of the experiments, the worms were cut into three 

 nearly equal parts as in Fig. A, a — h, c — d. These parts will be 

 spoken of as head-pieces, middle-pieces and tail-pieces. The 

 material was kept in covered glass dishes, somewhat shaded, and 

 the sea-water was changed morning and evening. 



Regeneration in general was much slower than in fresh-water 

 Planarians. The animals are very sluggish normally, and the 

 pieces moved but little even when disturbed by changing the 

 water, the head-pieces, however, being much more active than 

 the middle-pieces and tail-pieces. The tail-pieces continued to 

 deposit eggs for several days as freely as did the entire worms, 

 and the eggs developed normally. 



