558 R. 0. PUNNETT. 



most species of Eupolia (cf. 8, pp. 116 and 120, 10^ p. 577, 

 and 2, p. 44). 



The gonads in both the specimens sectioned contained 

 minute ova in various stages. They alternate with the 

 intestinal pouches, and open to the exterior by well-marked 

 ducts just above the side stems. The cavities in which the 

 young ova lie are not lined by any kind of epithelium, but 

 are merely somewhat indefinite spaces in the gelatinous 

 mesenchymatous tissue Pi'obably the ova arise from the 

 mesenchyme cells, as has been suggested hy Montgomery in 

 the case of Cerebratulus lacteus (6, p. 17). 



The brain is somewhat high in comparison with its length 

 (fig. 20). The side stems form a well-marked ventral com- 

 missure beneath the anus. The oesophageal connnissure and 

 nerves are small. The arrangement of the dorsal nerve 

 shows a peculiar feature (fig. 18). After rising from the 

 dorsal commissure it passes backwards for some distance 

 between the outer longitudinal muscle layer and the cutis. 

 It is not until the intestinal region is almost reached that it 

 dips down and joins the median dorsal thickening of the 

 nervous layer surrounding the circular muscle layer. The 

 median dorsal thickening just outside the circular muscle 

 layer is found in all Heteronemerteans springing from the 

 dorsal brain commissure there (Riickennerv of Burger [5, p. 

 363]). In Oxypoliathis nerve is well marked, but does not 

 reach forwards as far as the brain (fig. 18, nd.). The 

 arrangement in this genus finds a close parallel in Cari- 

 noma armandi (5, p. 364, pi. xiv, figs. 4 — 8). Apparently 

 the so-called median dorsal nerve of other Heteronemerteans 

 must be regarded as containing two elements : (1) the true 

 median dorsal nerve springing from the dorsal commissure, 

 and (2) a specialised thickened portion of the nervous layer 

 surrounding the cii*cular muscles. In Oxypolia both have 

 round them a few nuclei of what are apparently ganglion 

 cells. Just beneath the circular muscles in Oxypolia is 

 found the " untere Riickennerv." 



The cerebral organ is small and considerably flattened 



