172 



sec 



mu 



Figure 125: Strongylocentrotus droebachiensis (Burke, 1980). Sagittal section through the 



terminal podium of a juvenile. 



bnp — basiepithelial nerve plexus; cd — calcified disk; ct — connective tissue; mu — muscle 



layer of the podium; myc — myoepithelial cells; nr — nerve ring; sec — secretory 



cells; sen — sensory cells. 



;■■ -atch 



Figure 126: Sagittal section of the primordium of Peronella japonica (Okazaki and Dan, 



1954). 



A — early larva; B — late larva. 



am — amniotic sac; arch — archenteron; bl — remains of blastopore; c — coelom; 



g — rudiment of gut; h — hydrocoel. 



