566 THE AMERICAN NATURALIST [Vol. LI 



may be adhering firmly by its tube feet to the vertical wall 

 of the aquarium. When the constriction and separation 

 of the skin- and muscle-layers is completed, a short length 

 of the intestine usually remains for a time connecting the 

 two pieces ; it may rupture close to one of them, or may 

 disintegrate completely. The point to be noted is, that 

 the resultants of the division do not move apart, but re- 

 main quiescent. 



Lastly, after considerable searching, I found in the 

 field one case in which division had evidently just been 

 completed. The halves were still joined by an exposed 

 portion of the gut. 



On the basis of all this evidence there is certainly reason 

 to believe that Holothurin surinamensis, in the adult state, 

 normally multiplies its numbers by a process of binary 

 fission. The resulting organisms readily complete their 

 missing parts, but probably do not undergo a second divi- 

 sion until after the lapse of a considerable interval, if 

 they do at all. 



It would be of some interest to determine the nature of 

 the sexual products in the animals which thus result from 

 division. 



I Holothurian by Light. Amer. 



muda. Amer! Nat., Vol. 49, pp. 28-36. 



Zool. Jahrb., Abt^f. Physiol., Bd. 35, pp. 233-297. 

 Dalyell, J. G. 1851. The Powers of the Creator Displayed in the Creation, 



etc., Vol. 1, London, 286 pp., 70 pis. 

 Delage, Y., et H^rouard, E. 1903. Les echinodermes. TraiU de Zool. 



concrete, T. 3, x -f- 495 pp., 565 figs., 53 pis. 

 Lang, A. 1894, Lehrbuch der vergleichenden Anatomic der wirbellosen 



Thiere. xiv 4- 1197 pp., 8o4 Fig. Jena. 

 Morgan, T. H. 1901. Eegeneration. Columbia Univ. Biol. Sen, VII, 



I 



