278 



NEREIS PELAGICA 



green, and the palpi, tentacles, and tentacular cirri are pale green, the head itself being olive 

 with the white trifid mark posteriorly. The pelagic posterior region is developing, and 

 it is pale, while the feet are vascular. The ova are pale greenish with numerous large 

 globules amongst the smaller. 



The epitokous females hitherto observed are about the size of the males, though one 

 or two are larger, and all possess the triradiate band between the eyes and a pale peacock- 

 green colour anteriorly. The first five dorsal cirri are enlarged at the base and the 

 ventral cirri of the same feet are slightly swollen. In the altered posterior region the 

 dorsal cirri are also somewhat dilated towards the base (cirrophore), and have inf eriorly 

 on the enlarged region low papillae or warts, to which groups of stalked Infusoria and 

 also slender filaments of Algae adhere. Thus, although the prominent row of papillae 

 which projects from the lower edge of the cirrus in the male is absent, there is a tendency 

 to such growths. The ventral cirri present even a more marked tendency to these 

 growths, about four prominent cones being found on the ventral edge, and they also 



otn 



vfn 



Fig. 65. — Transverse section (made by Capt. F. H. Stewart, M.D.) of a nearly ripe Nereis, ov. Ova. 



The other letters as before. 



have Infusoria and Algae attached. The swimming bristles in the posterior region are 

 very large. Ventrally the same marked distinction between the anterior and posterior 

 regions of the body occurs as in the male, the anterior region being pale, a slightly 

 greenish shade only being visible in the head-region, whereas the posterior is of a 

 deep pinkish purple. This hue is apparently not due to the muscles, as during the 

 movements of the animal the intensity varies, as if from vascular changes. 



The heteronereid feet of the female agree generally in the position and shape of 

 the lamellae and other parts with the male. 



The changes which ensue in the body of the ripe female Nereis are indicated in 

 the accompanying section (Fig. 65). 



Two examples, about 5 ins. in length and apparently answering to this species in the 

 heteronereid condition, were procured by Mr. Gray in October, 1894, in the stomach of 

 a salmon at Berwick-on-Tweed. Both were females, still with a few dark-coloured ova 

 in groups at the bases of the feet. The condition of the jaws and paragnathi, which 

 were unusually large, showed that these were old specimens. 



