DEVELOPMENT OF CUCUMARIA ECHINATA 175 
hood is formed containing a mass of food-yolk of a green colour, 
The first pair of pedicels appear on the ventral side, and at this 
stage large calcareous plates, which differ in shape from those 
found in the adult, appear in the interradii. Next to the five 
primary tentacles (Text-fig. 1, I) three more (IL, II,, I,) arise, 
of which in most cases the right-hand one (II,) appears first. 
The larva attains about 2 mm. in length without having developed 
the two remaining tentacles (ITI). The manner of the branching 
of the tentacles seems to follow a certain rule, just as in the 
TEXxtT-FIG. 1. 
V 
Diagram showing the order of appearance of the tentacles. Anterior 
view. Larger circles (I) represent the primary tentacles; medium- 
sized (II), secondary ones appearing next ; and smallest ones (III), 
those last to appear. mes, =position of the dorsal mesentery. 
(After Mitsukuri.) 
phyllotaxis among plants, and the second pinnule is the largest 
of all (Text-fig. 2). 
‘The first pair of pedicels are followed by the third (Text-fig. 
3, 3) appearing on the left side of the midventral radius, then 
the fourth (4) appears on the ventral side of the right ventral 
radius. A further increase of pedicels may be seen in the diagram. 
To some extent the pedicels increase forwards from the height 
of the first pair, while later some appear behind it.’ 
The second report was contained in his address on the change 
