52 MORPHOLOGY OF 



larger granules or even masses of them are to be found in the 

 spaces surrounding them. 



The gland of the living B. salmoneus is light green in 

 colour. 



The nature of these glands is entirely obscure. These 

 yellow granules occur amongst nearly all the mesoblastic 

 tissues. In B. Robinii (collar) they may be found in the 

 fresh state, presenting the appearance shown in fig. 100. They 

 are never crystalline. 



An attempt was made to investigate the chemical nature of 

 these bodies, but with only negative results. They may, per- 

 haps, be excretory, and it is possible that they are more or less 

 removed by the proboscis pore and collar funnels respectively. 

 This does not explain their presence in large masses in the 

 trunk body cavity {v. fig. 93, a), from which no pore has been 

 observed to open. Occasionally granules of this character 

 occur in the ectodermic structures, suggesting that they are a 

 product of the activity of all the tissues. 



The proboscis pore was shown to arise at two gill-slits 

 as a small vesicle in the skin of the proboscis stalk upon the 

 left side {v. fig. 34) ; at three gill- slits it acquires an opening to 

 the exterior, and at four gill-slits its tissue fuses with the lining 

 of the left posterior horn of the anterior body cavity {v. fig. 99), 

 placing this cavity in communication with the exterior. 



In B. Kowalevskii this pore is permanently on the left 

 side of the body ; in B. rainutus, &c., it is median. 



The collar funnels arise as thickenings in the outer wall 

 yL of the ai'terial cavity opposite the opening of the first gill- slit 



'v. fig. 101). These thickenings soon become perforated 

 (8, g. s.). At their origin they are simple conical funnels, but 

 they soon acquire a crescentic lumen owing to a thickened 

 inward folding of their outer wall. This is not conspicuous in 

 B. Kowalevskii (cp. figs. 88 and 104). Their histology is 

 sufficiently indicated in the figures. 



As previously mentioned, the blood-vessels consist of 

 (1) a dorsal vessel leading from the heart to the tail; (2) a 

 ventral vessel running from the back of the collar to the tail ; 



