INCOMPLETE REGENERATION IN LEPTOPLANE LITTORALIS 193 



regenerate partially. The normal form and behavior of the 

 worm are restored, and the eye-spots are formed ; but 



5. The cephalic ganglia themselves never regenerate if com- 

 pletely removed. 



6. Regeneration of the anterior tip of the worm occurs in the 

 absence of the ganglia. 



7. Lateral regeneration occurs in the absence of the ganglia, 

 even though the ganglia themselves are not restored. It still 

 remains unexplained why in the polyclads the tissue posterior to 

 the cephalic ganglia does not regenerate the missing parts anterior 

 to their level, and why the tissue around the ganglia does not 

 restore them. It seems clear that the absence of the ganglia is 

 in some way directly responsible for the lack of anterior regenera- 

 tion, for when the ganglia are not entirely removed, complete 

 regeneration occurs. The completion of the form of the worm 

 and regeneration of eye-spots (though without the ganglia) in 

 experiments 1-5 may have come about mostly through lateral 

 regeneration, for in each case anterior tissue remained on one or 

 both sides. 



My work was carried out at the Marine Laboratory of Leland 

 Stanford University. It gives me pleasure to express my 

 appreciation of the courtesy extended to me while at Pacific 

 Grove. 



February, 1905. 



