106 Froceediiujs of the Royal Society of Victoria. 



the lateral vessels of Geonemertes, although 1 have been 

 able to tiiicl no external openings in the latter. 



There are so many points connected with the circulatory 

 and excretory system of Nemertines still involved in 

 ob8curitA\ that I may well l)e excused from attempting to 

 give a complete explanation of the structures described 

 above. I would merely suggest as a possible working 

 hyj)otliesis that in Geonemertes the excretory and circulatory 

 systems are even more closely related than usual, being in 

 fact represented by one and the same system of vessels, and 

 that jXKs.-iihly there are no external excretory openings. 



Figures 19 'to 23 illustrate the histological structure of 

 various parts of the va.scular and excretory systems as seen 

 in sections, and will, it is hoped, suliiciently justify the 

 statements made above as to the form and structure ot these 

 parts. For the convenience of com])arison all these figures 

 are drawn to the same scale. Figure 2(j, as already observed, 

 was drawn from life. 



It is obvious that the excretory system of Geoneniertes 

 differs vt^ry strikingly from that of marine forms, and it is 

 especially remarkable that it ditfei's even raoi-e from that of 

 its marine allies in the grouji Enopla than from that found 

 in the J ;k)/>/(f, foi", accoixling to Biirgei-,* the blood-vessels in 

 the marine Kiiopla, foi-m no dilatations nor capillaries, and 

 he could hud no connection between the blood-vessels and 

 the excretory organs. 



/. Nervous System 



The nervous system does not, so far as I have been able to 

 make out, present any striking peculiarities, and a brief 

 descri[)tion of it will therefore suffice. At the anterior end 

 of the body, immediately behind the mu.scular diaphragm 

 already noticed, is situated the l)rain, or cerebral ganglionic 

 mass (Figs. 2, 3, +, 5, 7). This consists of the usual ibur 

 l(^be.> iound in Nemertines, two on each side ot" ihe extreme 

 anterioi' end of the ])roboscis sheath. One of the two lobes 

 of either side is larger than the other and is also more doi'sal 

 and more anterior in position ; we ma}' call it the dorsal lobe 

 of the ganglion (Figs. 3, 4, 5, 7, (/-. <j) The other, smaller 

 lobe of eacli side is more posterior and ventral and may be 

 called the ventral lobe of the ganglion (Figs. 2, 3, 4, 5, 7, v. g) 

 The right and left ventral lobes are connected together by a 



* Loc. cit. 



