DEVELOPMENT OF CUCUMARIA ECHINATA 227 
The eighth is given out dorsad from the right dorsal radial 
canal, and the ninth and tenth arise ventrad from either the 
right or left ventral radial canal. Thus the ten-tentacled 
young of Holothuria has two tentacles on each inter- 
radius, but the dorsal paired radii have each only one, while 
the ventral paired radii have each three (Text-fig. 9, B). 
Pseudocucumis africanus, which is a_ twenty- 
tentacled form, remains while young in the ten-tentacled stage 
for a considerable period (Ohshima, 39, 1916). Here in this 
stage each radial canal sends out a tentacular canal on each side, 
just as in Cucumaria and different from Holothuria. 
According to Lud wig (24, p.97),in Phyllophorus urna, 
another twenty-tentacled form, the sixth and seventh tentacles 
appear between the dorsal and ventral pairs of the primary 
five, just as was known in C. planci. In the ten-tentacled 
stage of Ps. africanus of about 6-5 mm. in length, the 
relative sizes of the tentacles indicate, to a certain extent, their 
order of appearance, presumably agreeing with C. plane 
and C. echinata. 
Manner of Branching of the Tentacles. In one 
of my former papers (87, 1914) I described the manner of 
branching seen in the adult Cucumaria. Some passages 
may here be translated. 
‘Living specimens of C. echinata measure, in their fully 
extended state, up to 10 em. in length and 2 em. in diameter, 
and the tentacles attain about 4 em. in length. The pair of 
tentacles belonging to the mid-ventral radius are markedly 
smaller than the others. 
‘Hach of the eight tentacles, other than the ventral pair, 
gives out twenty-five to thirty side branches (first order), 
arranged in a dextrorse spiral, or turning “with the sun”’, with 
an angular divergence of one-quarter or 90°. The first branch 
(no. 1) stands at about 5 mm. above the base of the stem and 
on the right of the outside (as seen from outside). The second 
branch (no. 2) is the largest, standing on the left of the outside, 
No. 8 is markedly smaller, standing on the left of the inner side, 
and no. 4, also small, on the right of the inner side. No. 5, 
NO. 258 R 
