104 Proceeding.^ of the Royal Society of Victoria. 



granular substance. Tlie wall of the tubule between the 

 nuclei is visible as a fine, highly retractive outline. 



Although they are such obvious and definite structures in 

 properly stained preparations it is by no means easy to 

 decide upon the true nature of these intra-cellular tubules. 

 The position of the main branches and the connection 

 with the lateral vessels suggests that the former are the 

 homologues of the transverse vessels of other Nemertines. 

 Their histological structure and much biunched character 

 suggests that they are excretory in function. The excretory 

 system is so intimately connected with the vascular 'system 

 in other Nemeitines that I am inclined to believe that both 

 these suggestions may be correct. 



So far as I am aware no excretory system has yet 

 been described in land Nemertines, and it seems not 

 impossible that in Geonemertes the same system of vessels 

 is both excretory and circulator3\ Apparently the longi- 

 tudinal vessels are mei-ely specialised portions of the network 

 of tubules, being similar tubes with the addition in some 

 places of fine circular fibres and an external layer of vesicular 

 cells. Hence I believe the lumen of the longitudinal vessels 

 to be probably intra-cellular. 



The great objection to considering the network of tubules 

 as excretory is the apparent absence of any opening 

 whatever to the exterior. In other Nemertines such as 

 Polla the excretory pores are easily visible, and in the genus 

 mentioned I have had no difficulty in finding them in 

 transverse sections. Did such distinct openings to the 

 exterior exist in Geoner)iertes I hardly think that I could 

 have overlooked them. It is, however, very possible that 

 sjnaller openings exist which I have either overlooked 

 entii'ely or failed to distinguisli from the numerous genital 

 apertures to be described ))resently. 



For a long time, also, I could detect nothing of the nature 

 of flame-cells in Geonemertes, which one would certainly 

 expect to find in connection with such a system of excretory 

 tubules as I have described. Had I relied solel}^ on my 

 sections I should probably never have found flame-cells at 

 all, but in examining a crushed preparation of the living 

 worm I was fortunate enough to find a beautiful flame-cell 

 in full activity. This is represented in Figure 26, as it 

 appeared in optical section while alive. It will be seen that 

 at one end of the cell there is a triangular projection of 

 denser and clearer looking protoplasm ; the swollen middle 



