No. 609] MULTIPLICATION IN HOLOTHUBIANS 



564 



That the oral and cloacal terminations just described 

 do in reality represent regeneration, has been verified by 

 observation of the course of regeneration in the labora- 

 tory after experimentally cutting the holothurians (in 

 various ways (cf. Crozier, 1915&). Certain specimens 

 also have been tabulated as "regenerating"' when their 

 appearance (Fig. 2, c), backed up by dissection, suggested 

 that they had just completed division and had not yet 

 begun to regenerate. These specimens lacked either a 

 cloaca, or the stone ring and buccal structures, depending, 

 obviously, on their former relation to the complete indi- 

 vidual from, which they were derived. 



a b c 



FIG. 2. Outlines of individuals dividing or recently divided. In a and b 

 the division is shown in progress, x % ; in 6 the exposed portion of the undivided 

 Intestine is visible ; in c is given the outline of a recently separated oral half, 

 natural size. At x is seen a protruding bit of the portion of the respiratory trees 

 retained within this half animal. The characteristic puckering of the surface 

 at the division area is also indicated. 



The evidence that the regeneration found occurring 

 under natural conditions results from the self-division of 

 adult holothurians, involves two considerations. The 

 first concerns (a) the relative size of the regenerating 

 animals, and (b) the relative frequency of anterior and 

 posterior ends noted as regenerating. The second has to 

 do with direct observations of self-division. 



