‘DEVELOPMENT OF CUCUMARIA ECHINATA 209 
that J. Miller had observed in the young developed from 
‘ Auricularia mit Kugeln’ that the first pedicel was put forth 
on the right from the mid-ventral radial canal (Ludwig, 
21, p. 291). 
Primary Tentacles.—Now the five rudiments of 
primary tentacles can be referred to the respective interradius 
(Pl. 9, figs. 23.4,B; 24a-p; t,-,). No. 2 (é,) lies im the mid- 
dorsal interradius, no. 8 (ts) in the right dorsal, no. 4 (ty) in the 
right ventral, no. 5 (t;) in the left ventral, while the remaining 
one, no. 1 (t,), which should arise from the dorsalmost lobe, 
and is the last to appear, is in the left dorsal interradius. 
In their early stages the five primary tentacles arise directly 
from the ring canal, or more properly speaking, the hydrocoele 
differentiates into the tentacle-rudiments and the rig canal. 
In the course of growth a peculiar grouping of tentacles begins 
to appear in relation to the radial canals (Text-fig. 4, a—c). 
It seems very probable that the rudiments of the radial canals 
develop at the expense of the adjoining parts of the hydrocoele 
ring, attracting towards them the bases of the tentacle-rudiments, 
so that the latter seemingly become branches given out from 
the radial canals, totally independent of the ring canal. The 
srouping of tentacles is precisely the same as that found by 
Ludwig (22, pp. 188, 608) in C. planci, i.e. the ventral 
pair gather at the mid-ventral radius, that of the right dorsal 
interradius moves towards the right dorsal radius, and the 
remaining two meet with the left dorsal radial canal (Text- 
fig. 94, I, I’). Ludwig insisted upon the opinion that all 
the five primary tentacles appeared simultaneously as branches 
of the radial canals, not directly from the ring canal. One must 
keep in mind that Ludwig’s first observations were made 
on the eighth-day larvae, which are quite well established dolio- 
lariae, and that in his second report he tried to trace the fact 
as far back as to the fourth-day larvae. Ne wth (86, p. 687-8), 
confirming Selenka’s view, claims that the primary tentacles 
are originally interradial in position, arising from the rmg canal 
directly and alternating with the radial canals. He found that 
some individuals had shown on the third day that curious grouping 
