348 Charles Zeleny. 



In the winter and spring of 1902-03 with the above results in 

 mind two groups of experiments were undertaken to further test 

 this point. 



A comparison of the rate of regeneration of the arms in five 

 series of the brittle-star, Ophioglypha, with one, two, three, four 

 and five removed arms respectively, showed that excepting the 

 case where all five arms are removed and in which the animals 

 were dead or dying before the completion of the experiment, a 

 series with a greater number of removed arms regenerates each 

 arm faster than does a series with a smaller number of removed 

 arms. Thus with an increase in the degree of injury there is more 

 than a corresponding increase in the total amount of regeneration 

 in a given time. 



In the Crustacean, Alpheus, a result similar to that for Gela- 

 simus was found but with the addition of a quantitative deter- 

 mination of the actual rate which was not possible for Gelasimus 

 because of the slow rate of moulting in the latter. The Alpheus 

 data are, however, complicated by the fact that the two chelae 

 are of unequal size and undergo a reversal upon removal of the 

 larger one.^ The number of individuals available for the final 

 comparison was likewise small because a large proportion of the 

 specimens cast their chelae accidentally during the course of the 

 experiment.^ 



It seemed desirable, therefore, to test the results in a more con- 

 clusive way upon a form which does not have the complications 

 found in Alpheus and Gelasimus. The common crayfish, Cam- 

 barus propinquus, has chelae which fulfill the requirements of 

 such a form. They are equal in size and similar in character, are 

 cast off at a definite breaking joint upon injury to their nerves and 

 the animal does not readily throw off its appendages as a result 

 of the necessary handling incidental to the course of the experi- 

 ment. In one series the right chela alone was removed. In the 

 other series the two chelae and the last two pairs of walking legs 

 were removed. The resultant data show very conclusively that 

 in the series with the greater degree of injury each chela regenerates 

 more rapidly than the single removed chela of the series with the 



iPrzibram, 'oi, Arch. Entw. Mech., xi; Wilson, '03, Biol. Bull., iv; Brues, '04, Biol. Bull., vi; 

 Zeleny, '05, Journ. Exp. Zool., ii. 



^The description of the preceding experiments is given in Journ. Exp. Zool., vol. ii. No. I, Apr., 1905, 

 pp. 1-102, 



