MORGULIS. — REGENERATION IN THE BRITTLE-STAR. G59 



on his study of regeneration in the brittle-star Ophioglypha lacertosa. 

 He formulated his rule in these words : " The rate of regeneration of a 

 removed arm increases as the number of uninjured arms still remaining 

 decreases." According to my own observation specimens of Ophiocoma 

 pumila with 1 to 3 arms removed regenerate in the course of thirty 

 days new arms ranging in length from 10 to 11 mm., while those de- 

 prived of 4 or 5 arms regenerate arms from 10 to 13 mm. long. It 

 will also be observed that there was an equally rapid regeneration in 

 the two animals, one with all five arms cut off at the middle and the 

 other with one arm only thus cut off (Figures 7 and 11). 



It is evident from this that there is some correlation between the de- 

 gree of injury and the rate of regeneration, but that this relation is not 

 of the nature of a close parallelism, such as is suggested by Zeleny's 

 rule. Furthermore, it is stated that in Ophioglypha lacertosa "the re- 

 generated lengths are on the whole at least twice as great in Series IV, 

 where four arms were removed, as in Series I, where only one arm was 

 removed." This, again, differs from my results in Ophiocoma pumila, 

 where the regenerated lengths never presented such wide variations. 



