DEVELOPMENT OF CUCUMARIA ECHINATA 225 
now utterly disappeared. The axial sinus has given rise to the 
internal madreporite shaped like a folded leaf. A very peculiar 
feature is seen inthe young of C. ijimai. The ten-tentacled 
young of this species found in the mother’s brood-pouch measure 
about 5 mm. in length. No well-marked madreporie body can 
here be found, but the distal end of the stone-canal is 
dilated at reaching the dorsal body-wall into a flat cavity. 
The cavity extends posteriorly and ramifies like a root, each 
of these branches opening to the exterior. Delicate calcareous 
deposits are found at the junction of the canal and the flattened 
cavity, as well as in the wall of the canal. In the young of 
C. crocea MacBride and Simpson were able to find 
the opening of the pore-canal. According to Ludwig (22, 
p. 186) the pore-canal of C. planci loses its opening on the 
eighteenth to twenty-fourth days, and until the ninety-eighth 
day the axial sinus opens to the body-cavity through its thin- 
walled side. The canal of Phyllophorus urna remains 
longer than in C. planci (Ludwig, 24, p. 98; see also 
Russo, 44, p. 42). 
Secondary Tentacles. Ludwig (22, p. 184) found 
two more tentacles added to the primary five by the one hundred 
and sixteenth day. These were sent out dorsad from each of 
the lateral ventral radial canals. He was, however, unable 
to observe actually the successive appearance of the remaining 
three. He only assumed that the eighth should appear dorsad 
from the right dorsal radial canal, the ninth and tenth ven- 
trad from each of the lateral ventral radial canals. According 
to Mitsukuri (ante, p. 175) the first to appear among the 
secondaries in C. echinata is that given out from the right 
ventral radial canal. 
From observations on some specimens at my disposal I can 
corroborate Ludwig’s view. In some specimens, as is seen in 
no. 10 of Table III, there are only eight tentacles where the sixth 
and seventh have attained a size equal to the primary five, but 
the eighth, which appears dorsad from the right dorsal radial canal, 
is distinctly smaller. Thus Mitsukuri’s second statement, 
contradicting his first one, is obviously a mistake. Among 
