504 I. IKEDA : 



not discover any l)lood vessel in Acilnofrocha ; lie thonglit that 

 the blood vessels of the metamorphosed worm arose in the cor- 

 pnsele masses of the larva. 



Claparède ('63) mentioned a rino-like vascular canal nnder 

 the tentacalar row of the larva, hut did not explain its nature. 



Schneider ('62) discovered two vessels in Actinoiroclid, which 

 ran parallel aloni;- the mid-dorsal line of the stomach. 



jMetsciinikoff ('71) descril)ed and figured in a larva of 10 

 tentacles the "feinen Häutchen" situated just ahove the invagina- 

 tion pou<'h, Avhich was said to 1)e the " Gefässanlage." Besides, 

 it is stated that he saw a ventral " sinusartigen Schlauch " which 

 covered the greater part of the stomach and communicated an- 

 teriorly with the collar cavity. According to his view, this 

 Schlauch should give rise to the ring vessel of the adult. But 

 what are really meant hy the " Schlauch " and the " Häutchen " 

 is not clear from his text and figures. 



Wilson ('81) confirmed the main points of Metschntkoff's 

 observations, l)ut disproved the 25i"^^ence of a blood vessel along 

 the intestine, and also the free communication between the pseudo- 

 hœmal space and tlie perisviceral cavity. According to this author, 

 there are two sorts of corpuscles : the one kind floats in masses in 

 the perivisceral cavity, and the other (the pseudohœmal corpuscles) 

 arise within the cavity of a sinus which is formed in the stomach 

 walls and form the circular ring vessel of the adult. 



Caldwell ('82-'83) gives us a concise description of the 

 vascular system in Actinofrocha and in its adult form. He says 

 that the corpuscle masses " arise fro/n the me^ohlast cells in front 

 of the septum,^^ and that " The vessels arise as slits in the 

 splanchnopleure. The adult condition is reached partly hy con- 

 strictio7is, parthf hy out-yroirth from these. Thus v;e have at the 



