444 



Charles R. Stockard 



at different levels. The extent of injury is the same in all indi- 

 viduals. 



Forty-nine days after the operation the specimens w^ere killed, 

 fully extended in chloretone and measured. Tables I and II 

 contain the results of the measurements. The tables show that 

 the arms have regenerated from 25 mm. to 50 mm. in length. 

 Such a length makes the error in measurement slight. 



TABLE I 

 Rates of arm regeneration at di^erent levels in the brittle-star, Ophiocoma echinata 



♦Regenerated portion broken and not measured. 



The averages for Ophiocoma echinata (Table i) show that the 

 nearer the disk the arm is amputated the more rapidly will the 

 subsequent regenerative growth proceed. The arms cut i cm. 

 from the disk have grown new buds averaging 35.8 mm. long. 

 The specific amount of regeneration obtained by dividing the 

 length of new tissue by the disk diameters is 2.08. Comparing 

 the average growth from arms cut 5 cm. from the disk, the actual 

 amount of tissue grown is 26.9 mm. or only 75 per cent as much 

 as from the i cm. stump and the specific amount is 1.57 against 



