56Ö i. iivEDA : 



corpuscles a})})cur us the gigantic inesoblast cells in the Ixxly-cavity 

 of the larva with one or two ]>airs of tentacles (iig, 44, coi'p.). These 

 cells may be easily distinguished from other wandering mesohlast 

 cells in that tliey have an enormous size and are loaded with an 

 abundant (juantity of large yolk grains. Xow in 8-l()-armed 

 larvic of type ^4, not only such peculiar cells but also the so-called 

 corpuscle masses can not be found in any pai4 of the l)ody- ' 

 cavities. Instead of them the cobar cavity and often also the 

 tentacular cavities contain a few large and isolated mesohlast cells 

 Avhich closely resemble in size and structure the blood corpuscles 

 of a highly advanced larva. These cells no longer contain lai'ge 

 volk o-rains, but enclose numerous hue, refriuirent <>ranules. Fig. 

 4(3 represents two such corpuscles [corp.) floating in the tentac- 

 ular cavity [i.) of a larva of 10 tentacles. It can with pro- 

 priety, I believe, l)e admitted, that these corpuscles have arisen 

 by repeated division from the gigantic mesohlast cells, whose yolk 

 contents have been gradually used up during the })]'ocess. If this 

 be not the case, then how is the presence of those isolated cor- 

 puscles in the young larvœ to be explained ? If, as is imagined 

 by Caldwell, they are produced by cell-nudtiplication taking- 

 place in certain parts of the si^anchnopleuric walls and form the 

 corpuscle masses from the lirst, why should such freely floating 

 and isolated corpuscles he actually preseid in the young larvai in 

 which the masses are not yet discennble ? i^o far as I know, in 

 the lai'VcC of tyj)e ^I, the corpuscle masses do not exist until the 

 animal has so far developed as to })ossess at least 14 tentacles 

 (Iig. 1)5, Corp.). At the stages of 14 and 10 tentacles, these masses 

 are present commonly in two }>airs, the one covering the stomach 

 diverticulum and the other just in front of the se])tum and on 

 both sides of the stomach (Iig. lo, corp.). Idiey appear as pinkish 



