12 ox A NEW SPECIES OF ENTEROPXEUSTA, 



transversely outwards, reaucing the lateral walls of the blind sac 

 to a thin layer, m hile the hind and middle portions of the wall 

 are somewhat thicker, as in Ft. minuta. From the transverse 

 lumen of the blind sac there passes forwards laterally a short horn 

 on each side (fig. 9, lh.)\ a section passing through the proboscis 

 neck just anterior to the passing down of the ventral blind sac 

 lumen thus shows three cavities in the notochord (fig. 9), two ventro- 

 lateral belonging to the horns of the ventral blind sac lumen and 

 a median situated near to the dorsal side of the notochord, the 

 main notochordal lumen now considerably reduced in size and with 

 numerous gland cells opening into it. Anteriorly the lumen 

 comes to occupy a more nearly central position (fig. S, div.)\ it 

 finally becomes reduced to a narrow slit (fig. 4, div.), which can 

 be traced to a slightly varying distance from the apex of the 

 notochord (fig. 14, div.). The lumen varies somewhat in position 

 and shape in different individuals, being in some situated nearer 

 the dorsal side, in others nearer the ventral side of the notochord; 

 its outline also varies — it may l)e circular or form a narrow 

 vertical or horizontal cleft. The lumen in this species has on the 

 whole a more median position than in Ft. minuta , and con- 

 sequently the dorsal and ventral walls are more nearly equal in 

 thickness. In fig. 14 the lumen of the notochord is represented 

 somewdiat diagrammatically as a continuous wide canal, but as in 

 Ft, minuta it is interrupted by occasional bridges of tissue, and 

 also as in that species the dorsal wall of the lumen is smooth, 

 Avhile into the ventral there project short processes of the lumen 

 (fig. 14, div.). AVith the exception of the anterior part of the 

 lumen numerous gland cells open into it, testifying to the epithe- 

 lial nature of the whole structure. Numerous gland cells exist in 

 the dorsal wall of the neck portion of the notochord and they 

 extend for a considerable distance into the head region, l^eing 

 specially abundant round the part of the lumen situated just 

 anterior to the point of origin of the ventral ])lind sac lumen. 

 The lumen is, in some jDreparations, almost filled up by a diffusely 

 staining network, apparently derived from the secretion of the 

 gland cells opening into it. Numerous elongated cells, between 



