565 THE AMERICAN NATURALIST [VOL. LI 



One hundred H. surinamensis collected in Fairyland 

 Creek ranged in length from 6 to 18 cm., with the mode at 

 14cm. The regenerating specimens ranged in length 

 from 4 to 9 cm., with the mode at 7 cm. While no numer- 

 ically exact argument can be based on these figures, since 

 the length of any one holothurian is variable, the fact does 

 stand out that the regenerating animals are about one 

 half the length of the non-regenerating ones. There is 

 also the significant fact that not a single instance has been 

 found in which both a (supposedly) new oral and new 

 cloacal end were present. If self-division has occurred, 

 then we should expect to find new oral and new cloacal 

 extremities in equal frequency; among the rather small 

 number of cases available, we find their ratio to be as 

 1:1.17, an agreement sufficiently close to favor belief in 

 self-division. 



The evidence concerning the second point is even more 

 conclusive. I have seen, in all, nine cases in which a holo- 

 thurian (H. surinamensis}, in the laboratory, divided 

 itself into two parts. The animals concerned seemed 

 healthy, and bore no visible signs of having been in any 

 way injured. In no case did the halves so formed redi- 

 vide, although in two cases the resulting portions lived 

 in the laboratory for a month (Aug. 3 to Sept. 5, 1916), 

 during which time, even in the absence of food, missing 

 structures were regenerated. 



In one case the process of division occupied five days; 

 in another, twenty-four hours. Probably it is executed 

 more rapidly in the field. The details of the division were 

 not notably different from those described by Chadwick 

 (1891) for Cucumaria, except perhaps in one particular. 

 The intestine is not drawn out between the separated 

 halves, as found in Cucumaria and as I have observed 

 in the young of H. captiva. Division begins* midway of 

 the length of the body with a deep insinking of the " dor- 

 sal' bivium. A powerful circular constriction, accom- 

 panied by some slight local disintegration of the integu- 

 ment, completes the separation (Fig. 2). During the 

 progress of division the animal is quiescent, although it 



