On an Australian Land Nemertine. 97 



divided by a sligl.t transverse constriction into two portions 

 (Fig. 15), an anterior, whicli seems, as pointed out by von 

 Graff, to belong more properly to the eversible portion of.tlie 

 proboscis, and a posterior, wliicli seems to belong to tlie non- 

 eversible portion. For the sake of convenience, however, I 

 follow von Graff in considerirg these two portions together 

 as a separate region of the proboscis, the stylet-region. In 

 longitudinal sections, however (Fig. 15), the two poi-tions of 

 the stylet-region are seen to be even more sharply marked 

 off from one anothei- than appears from the outside. 



The structure of the anterior half of the stylet-region is 

 vei'y complicated. If we take a transverse section across it 

 (Fig. 16) we shall see that it is nearly solid. In the centre 

 is a deeply staining, homogeneous mass (Fig. 16, h), circular 

 in outline; this is the so-called "handle" of the stylet, which 

 appears to be of the nature of a secretion. This handle is 

 surrounded by a rather thin layer of radiating muscle (?) 

 fibres, attached to the " handle " at their inner extremities. 

 Outside this layer of radiating fibres comes a rather thin 

 laN'er of circular fibres, interrupted at one side of the handle 

 by the •'poison-duct" [[). d.), which contains a granular 

 material. The boundary between the layer of radial muscles 

 and the circular layer is very sharp and distinct and gives 

 one rMther the impression of being the wall of a cavity across 

 which the radial fibres run to their insertion in the handle 

 of the stylet. The layer of circular fibres is not very regular, 

 and is seen in longitudinal section (Fig. 15) to be more or 

 less interrupted by i-adial bands, it is thicker behind the 

 handle of the stylet than around it. Outside this circular 

 la3^er is a very thick layer of longitudinal fibres interrupted 

 by occasional radial bands. The proboscidean nerve sheath 

 appears to die out in this region of the proboscis, but if I am 

 not mistaken it ma}' be traced as fai' back as the level of the 

 handle of the stylet (Fig. 16). Outside the thick la3^er of 

 longitudinal muscles is a layer of large, irregular, highly 

 granular and deeply staining cells (Figs. 15, 16, gl. z). 

 These evidently correspond to the layer of pigment granules 

 desci'ibed and figured by von Graff' in the case ot 

 Geonemevtes chalicopJtora, but I do not think that in our 

 species they are actually pigmented although their highly 

 granular character gives them a dark appearance under the 

 microscope even in unstained preparations. Lines of 

 granular material radiate inwards from these cells towards 

 the handle of the stylet, and altogether they appear to be of 



