The fore limbs grow simultaneously, and even more rapidly, but remain concealed within a diverticulum of the branchial chambers until fully formed, when they burst through the skin (unless the left spiraculum be utilized for the egress of the corresponding limb).
From the cephalic part of this primary diverticulum solid rods of cells called the hepatic cylinders grow out, and these branch again and again until a cellular network is formed surrounding and breaking up the umbilical and vitelline veins.
This diverticulum contains the blood-vessel and muscle-fibres (fig.
Portion of which the ova or spermatozoa are developed, the lower portion serving as an oviduct or vas deferens; the female generative organs open at the middle of the body, the male close to the posterior extremity into the terminal portion of the alimentary canal; from this cloaca a diverticulum is given off in which are developed one to three chitinous spicules that subserve the function of copulation.
In the Metanemertini there is a curious diverticulum of the intestine which stretches forward in the median line, ventral to the socalled stomach.
An anterior median diverticulum of the pharynx (fig.
J, Diverticulum on rectum.
And here also is a small diverticulum of b, Vaginal portion of the the duct f.
The small arm-sinus runs along the arms of the lophophore at the base of the tentacles, and gives off a blind diverticulum into each of these.
In the same region of the body, namely, close behind the pharynx, a large diverticulum is given off from the ventral side of the gut.