342 Transactions. — Zoology. 



free surface of the intestine, goes to the test. Along the dorsal 

 free edge of the branchial sac runs a large vessel, to which 

 radiate from the ventral edge of the branchial sac the large 

 transverse vessels. The posterior end of this vessel, on reach- 

 ing the gullet, divides into several vessels, of which one passes 

 along the free edge of the gullet and stomach, and joins (after 

 giving off branches to some of the stems of the digestive gland) 

 the vessel that goes to the test. Another vessel from the 

 dorsal branchial vessel runs along the attached side of the 

 gullet, and joins the dorsal vessel just before its division. The 

 anterior end of the dorsal branchial vessel joins the mantle in 

 close relation to the brain. From the branchial sac to the 

 mantle, the gonads, the intestine, the digestive gland, pass very 

 numerous vessels, which serve also as suspenders to keep the 

 lateral portions of the branchial sac in position. 



Of the vessels to the test, that on the right side (which I 

 mentioned as leaving the ventral vessel at the point where the 

 endostyle makes its dorsal bend) runs directly into the stalk. 

 The left vessel (which, as before stated, leaves the body about 

 midway between the anterior and posterior ends from the 

 vessel passing across the stomach) runs forward, turns 

 gradually dorsalwards, enters the stalk along with the vessel 

 from the right side, both vessels running right down the stalk. 

 Both these vessels in their course through the test give off 

 vessels, in their turn giving off smaller vessels, which finally 

 break up into terminal twigs, ending in little dilatations or 

 bulbs. These twigs are more closely aggregated in connection 

 with the external surface. A transverse section of the stalk 

 shows the same arrangement as in the test — the vessels break 

 up into small twigs ending in dilatations or bulbs, two twigs 

 usually opening into one bulb (as in the test). 



The anterior prolongation of the body, which is full of 

 blood-vessels, gives off chiefly one large vessel, which after a 

 time unites with one of the vessels from the test. 



E. Bcproductive Organs. 

 Gonads consist of a double series of somewhat rectangular 

 blocks attached along the body-wall of each side. When I 

 say "somewhat rectangular" I refer to the fact that the 

 larger gonads, at least, are more pyramidal in shape, with the 

 apex attached. The free surface of the larger gonads is also 

 often deeply marked by folds or creases. In young specimens, 

 or those not sexually mature, the gonads are of a light-cream 

 colour, but in sexually mature individuals during most of the 

 year they are of aii olive-green colour. Each cut in section 

 shows a central white mass — the spermary — with the green 

 part — the ovary — wrapped completely round it. The green 

 colour of the gonads changes in spirit first to a pink, then 



