254 Prof. M'lutosh's jS\)tes from the 



fjranular cells with fine connective-tissue fibres at certain 

 ]Kirts, besides blood-vessels. Tlicn a narrow pale belt 

 i)ecomes distinct within tlie circular fibres and basement- 

 tissue of tlie oral wall, apparently corresponding to the 

 pale sensory layer of Oivenia in the same region. The 

 nerve-centre appears as a narrow pale granular band in 

 section at the inner border of the hypodcrm of the body- 

 wall, and stretching downward from the dorsum (PI. XI. 

 tig. 2.2) as it passes by-and-by into the trunks connecting 

 it with the ventral cord. This region therefore represents 

 the prostomium, though devoid of any external indication. 

 The minuteness of the nerve-centre in comparison with that 

 of Oiceu'ta renders its finer details obscure, and it is more 

 tra)isparent. No fine strands from the hypodcrm could be 

 made out, the slightly prominent cells and interstitial tissue 

 alone appearing at the edge, whilst its inner border rested 

 on a smooth basement-tissue. Its ])Osition and extent 

 agree with that in (hvenia. 



In horizontal (longitudinal) sections the central nervous 

 system appears as an area at the inner border of the hypo- 

 derm about the point of the V-shaped oral funnel (PI. XI. 

 fig. 23), and its transverse breadth is shown by its appearing 

 on each side in these sections. So far as can be ascertained 

 in the preparations, no special sensory apparatus is present 

 either in the form of a groove or deposit of pigment in the 

 body-wall, but the pigment may have been removed by 

 long })reservation in spirit. Therein it differs from Owenia 

 with its j)ignicuted cells and its groove. 



Then, the hypoderm, again, extends over the Avhole depth 

 to the basement-layer dorsally, and the nerve-cords are 

 differentiated laterally — at first high up, nearly on a level 

 with the dorsal arch of the mouth (PL XI. fig. 25), and 

 then gradually descending as in Owenia. Very soon 

 between the mid-dorsal and the oral walls a blood-vessel 

 appears, and one in each lateral space, the connective-tissue 

 strands and cells which connect the Avails apparently 

 keeping them more or less in position, the vessels being 

 proportionally large for the size of the annelid and perhaps 

 subserving respiration (PI. XI. fig. 25 and PI. XII. fig. 24, 

 hv.). When the body-wall becomes continuous — that is, 

 just behind the ventral (oral) slit — the cords have reached 

 the commencement of the lower third of the body-wall, and 

 the median arch dorsally and the mid-lateral regions of the 

 gullet present the thickest layer of cells, the upper angles 

 and the lower edges being thinner. jMoreover, a section of 



