561 THE AMERICAN NATURALIST [VOL. LI 



many-armed creature relatively deficient in morpholog- 

 ical centralization; whereas in Cucumaria and in Holo- 

 thuria the body is compactly built, the animal much more 

 of a unified individual. Consequently the self-division of 

 these holothurians is not without interest, especially since 

 in these cases the plane of separation is anatomically per- 

 pendicular to that employed among the astroradiates, and 

 it is the purpose of this paper to present evidence which 

 proves that adult specimens of at least one species, Holo- 

 thuria surinamensis Ludw., do as a matter of fact divide 

 transversely into two parts under conditions which must 

 be regarded as normal. Since these divisions are not in- 

 frequent in large numbers of specimens, if not in a single 

 life-history, we must conclude that fission represents a 

 regular means of mutliplication in this species. 



A few years ago I found (Crozier, 19156) that about 

 10 per cent, of the examples of H. surinamensis which 

 were studied showed a condition of either the oral or of 

 the cloacal end which on the basis of observed regen- 

 erations following experimental cutting I interpreted 

 as representing regeneration, possibly as a consequence 

 of spontaneous self-division. Similar conditions have 

 been noted by others for some other species of holo- 

 thurians, e. g., by Benham (1912, p. 136) for Actinopyga 

 (Mulleria) parvula (Selenka), but they have usually been 

 referred to regeneration after injury by such bottom feed- 

 ing fishes as small sharks. Dr. H. L. Clark informs me 

 that he has found a corresponding state of affairs in some 

 Australasian holothurians, at least in regard to the oc- 

 currence in nature of specimens showing posterior re- 

 generation. 



I subsequently obtained young individuals of H. cap- 

 tiva Ludw., about 6mm. in length, which were observed 

 to divide spontaneously in the laboratory (Crozier, 1914, 

 p. 18), precisely according to the procedure figured by 

 Dalyell (1851) and by Chadwick (1891). Only a single 

 adult H. captiva has been discovered, however, in which 

 there was evidence of normal regeneration; this indi- 



