96 Proceedings of the Roi/al Society of Victoria. 



much the largest, (2) the stylet-region (Figs. 14, J5, *^. r.) 

 and (3) posteriorly, the non-eversible portion (Figs, li, 15, 

 n. e. r.) 



The eversible portion is a long, cylindrical tube, attached 

 all round at its anterior end to the proboscis sheath and 

 composed, from without inwards, of the following laj'ers 

 (Fig. 1(5) : — (1) a delicate epithelium, (2) a very thin layer 

 of circular muscles (e. c. 'm.), (3) a very thick layer of longi- 

 tudinal muscles (e. I. m. aiid i. I. m.), (4) a thickish layer of 

 circular muscles (I. c. on.), (5) a sub-epidermic layer (" base- 

 ment membrane") of hyaline, faintl}^ staining material 

 containing small, scattered nuclei, (6) a layer of glandular 

 ejntlielium {ijl. p.) elevated into numerous elongated papilla* 

 which project into the lumen of the I'etracted proboscis, 

 and into each of which the basement membrane is continued 

 as a more or less distinct core. The longitudinal muscle 

 layer makes up by far the greater part of the thickness of 

 the proboscis wall and is divided into two portions, an outer 

 thinner (e. I. m) and an inner thicker (i. I. m.), by the remark- 

 able nerve sheath of the proboscis {p. n. s.), which may be 

 conveniently described in tiiis place. 



The appearance of the proboscidean nerve sheath in trans- 

 verse section is shown in Figure 10 (p.v.s.) It is composed 

 of a finely granular, faintly staining material (? v.dth a few 

 scattered nuclei) and appears to form a continuous layer. 

 This layer is thickened at frec^uent and fairly regular 

 intervals to form a circle of stout longitudinal nerves, 

 continued outwards as thin, radiating, vertical plates to the 

 outer circular muscle layer. On their inner aspect the longi- 

 tudinal nerves are rounded off but occasionally give off small 

 branches towards the inner circular muscle layer. Similar 

 small branches are given off from the portions of the sheath 

 between the longitudinal nerves. 



This complicated |.)roboscidean nervous .sj^stem thus agrees 

 p"etty closely with what von Graff has described and figured 

 for Geonennertes cludicopJioru. Hubrec'ht* has traced tliis 

 nervous system into connection with the cerebral ganglia, but 

 I have not succeeded in doing this, though 1 have no doubt 

 that such a connection exists. 



The stylet-region of the proboscis is recognisable externally 

 as a distinct swelling at the junction lietween the eversible 

 and non-eversible portions (Fig. 14, st. r.) This swelling is 



* Vide Encijclopcedia Britunnica, Ai'ticle " Nemcrtiues." 



