100 Proceedings of the Royal Society of Victoria. 



are not nearly so strongl}^ developed. I have only been able 

 to detect two thin muscular la\^ers, an outei' circular and 

 an inner longitudinal. On the outer surface there appears to 

 be as usual a low epithelium, but I have not succeeded in 

 making it out at all clearly. Internally this portion of the 

 proboscis is lined by a highly glandular, ver}' darkly 

 staining epithelium, which I have not been able to clearly 

 differentiate from the darkly staining secretion which fills 

 tilt! lumen. At its posterior extremity the proboscis becomes 

 very narrow and ends blindly. To the blind end is attached 

 a strong bundle of long muscle fibres, the retractor muscle 

 (Figs. 13, 14, v. 'in.), which has its origin on the inner surface 

 of the dorsal wall of the proboscis sheath, a little in front 

 of the blind ending of the latter. When the proboscis is 

 retracted the retractor muscle is short and broad but it is 

 obviously capable of great elongation. 



It is, perhaps, hardly necessary to explain the mode of 

 action of the proboscis any further than has been already 

 done. Figure 14, taken from an actual dissection, represents 

 the entire proboscis, with its retractor muscle, separated 

 fi'om the body and in a partially everted condition. It is 

 hoped that reference to this figure will render further des- 

 cription unnecessary. The general view that the protrusion 

 of the proboscis is eflf'ected by the powerful contraction of 

 the muscles of the proboscis sheath, acting through the fluid 

 which surrounds the proboscis, while withdrawal is effected 

 by means of the retractor muscle, is doubtless correct. Pro- 

 bably the withdrawal is assisted by the contraction of the 

 muscular diaphragm (Figs. 2-6, m. d.), already described, 

 in connection with the anterior attachment of the proboscis 

 to its sheath. 



e. Circulatory and Excretory System. 

 The vascular system is very difficult to make out 

 thoroughly, as, owing to the size and opacity of the body, 

 it must be studied by means of serial sections. There are, as 

 in Geonemertes clialicopkora, three main longitudinal vessels, 

 one (dorsal or median) lying between the proboscis sheath 

 and alimentary canal, and one (lateral) on either side of the 

 body in the neighbourhood of and venti'al to the lateral 

 nerve cord.s. 1 have not succeeded in demonstrating any 

 connection between these vessels, unless the network of 

 excretory tubules, to be described presently, be considered 

 as such. 



