492 HIROSHI OHSHIMA 
EXPLANATION OF PLATE 21. 
(All figures were drawn by means of a camera lucida and magnified 
200 times.) 
Fig. 1.—Dorsal view of a young two-armed larva, in which the rudiment 
of the aboral spike (ab) has just appeared. (An unusually long process 
is seen arising from the base of the right post-oral rod.) 
Fig. 2.—Dorsal view of an old two-armed larva to show the fusion at 
the tips of the ventral horizontal rods (vk). (The posterior ends of the 
body-rods, br, are not overlapping here as normally.) 
Fig. 3.—Dorsal view of a young four-armed larva to show the fusion of 
the posterior ends of the recurrent rods (ve). The body-rods (br) are 
also fused with each other (hidden behind the aboral spike, ab). 
Fig. 4.—Left-side view of the same specimen as shown in fig. 3. A 
rectangle is formed by the body- (br) and recurrent rods (re). (From 
the base of the aboral spike an additional process is given out ventrally.) 
Fig. 5.—Dorsal view of an old 4-armed larva, in which the rudiment 
of the dorsal arch (da) has appeared and the posterior ends of the body-rods 
have begun to degenerate. 
Fig. 6.—Right-side view of a young six-armed larva to show the early 
stage of the postero-dorsal rod (pd). (The left recurrent rod, re, is here 
seen abnormally split into two.) 
Fig. 7.—Dorsal view of a twelve-armed larva. The body- (br), recurrent 
and ventral horizontal rods (vh) have all lost their connexion with the 
fellows of the other side. (The right dorsal horizontal rod, dh, is abnormally 
doubled. ) 
Fig. 8.—Right-side view of the same specimen as shown in fig. 7, to show 
the calcareous plate formed between the body- (67) and recurrent rods. 
ABBREVIATIONS. 
ab=aboral spike; ad=antero-dorsal rod; al=antero-lateral rod ; 
br = body-rod ; c= dorso-ventral connexion between body- and recurrent 
rods ; da=dorsal arch ; dh=dorsal horizontal rod; pd=postero-dorsal 
rod; pl=postero-lateral rod; po=post-oral rod; pr=pre-oral rod; 
re=recurrent rod; vk=ventral horizontal rod. 
