42 REGENERATION 



A somewhat similar result is obtained when an incision is made in 

 the side of the body of a planarian. A lateral head may grow out 

 from the anterior edge of the cut-surface, as shown in Fig. 17. 



It has been shown by Loeb that if the incurrent siphon of the ascid- 

 ian dona intestinalis be partially cut off, new eye-specks develop 

 around the margin of the cut, as shown in Fig. 18, A. I have repeated 



FIG. 18. A. After Loeb. Anterior end of Ciona intestinalis with oral-siphon partially cut off. 

 Eye-specks regenerate, both on oral and aboral edge. B. Same (after T. H. M.), showing 

 similar result on excurrent siphon. 



this experiment and obtained the same result, and found, as had 

 Loeb also, that the same holds true for the excurrent siphon (Fig. 

 1 8, B\ In these cases the new eyes appear both on the anterior 

 and posterior edges of the cut. Most probably the result is con- 

 nected with an external stimulus, rather than with an internal one. 

 This may be true also for cerianthus, but probably not for the 

 planarian. 



