

FIG. 35. Sycon gelatinosum. Transverse section through the wall of a cylinder 

 (parallel with the course of the canals), showing one incurrent canal (1C), and 

 one radial canal (R) throughout their length ; sp. triradiate spicules ; sp'. oxeote 

 spicules of dermal cortex (dc.) ; sp" . tetraradiate spicules of gastral cortex (gc.) ; 

 ec. ectoderm ; en. endoderm ; pin. pore membrane ; p/>. prosopyles ; ap. apopyle ; 

 di. diaphragm ; e.vc. excurrent passage ; P.G. paragastric cavity ; em. early 

 embryo ; em', late embryo. The arrows indicate the course of the water through 

 the sponge. 



