NEREIS DIVEBSICOLOR. 323 



the eyes, which are definitely formed on each side, the anterior pair being somewhat larger 

 and furnished with lenses. The frontal tentacles and the palpi are well formed and show 

 numerous fine palpocils, the mobility of the distal segment of the palpi being noteworthy. 

 The two pairs of tentacular cirri are now much longer, the dorsal stretching outward like 

 fine hairs as the animal pushes its snout forward. They retain the proportions to each 

 other as in the adult, though they have not yet reached full development in any case. 

 The ventral of each is considerably shorter than the dorsal, but projects clearly on each 

 side, the first rather longer and thicker at the base than the frontal tentacles. The body 

 is now elongated, having from sixteen to twenty bristled feet, and is marked along the 

 centre by a yellowish or brownish streak, often slightly moniliform or zigzag from the 

 intestinal contents, and a whitish dot is observed in some at the bases of the feet. The 

 massive and somewhat ovoid proboscis has six teeth behind the great anterior fang, and 

 the narrow part of the canal behind it is usually firmly contracted (and empty). The 

 first part of the gut behind the post-proboscidian narrow region is the largest, and for 

 some distance it is not marked by lateral constrictions, as in the succeeding portion. 

 Most of the feet anteriorly present a condition approaching that of the adult, though the 

 dorsal cirrus is shorter. Only the last two feet are devoid of bristles externally. The 

 caudal cirri are considerably longer. The circulation of the reel blood in the dorsal and 

 ventral trunks is now evident. The segmental organs extend backward to the posterior 

 feet, though not quite to the tail. 



So far as observed at St. Andrews, therefore, there is no foundation for the statement 

 that the Scotch representatives are hermaphrodite, and still less that they are viviparous, 

 as mentioned by Max Schultze, by the i Cambridge Natural History,' and by Gravier. 

 Max Schultze 1 gives a circumstantial account of finding female examples in April at 

 Greifswald with ciliated eggs and pear-shaped larva3 in the body-cavity, and he figures 

 two of the latter, hundreds of which occurred in the cavities at the bases of the feet. 

 His figures, however, give rise to doubt as to the nature of the ciliated forms, which have 

 the narrow end of the pear anteriorly with the two eyes at some distance behind it. In 

 one, indeed, the mouth is indicated behind the eyes as a small radiated disk. The 

 posterior end of the larva is broad and rounded. In the light of the condition at St. 

 Andrews doubt arises as to correctness of the interpretation, more especially in view of 

 the structure of the larva; but it is right to give a margin for possible variations in regard 

 to internal fertilization under certain circumstances. Yet it seems unlikely, and De St. 

 Joseph 2 is of the same opinion. 



The foregoing interpretation as to the mode of reproduction would seem to be most 

 in accordance with observation, since on the 28th May masses of clayey mud brought from 

 the habitat of the species and with the annelids in situ showed many free ova amongst 

 the mud coating the walls of the tube, and, further, various post-larval examples. 



In connection with the reproduction of Nereis interesting experiments have been 

 carried out by Loeb and Fischer, in which they found that the unfertilized eggs of Nereis 

 limbata developed into swimming larvae by keeping them for some time in sea- water 



1 ' Amer. Journ. Physiol./ vol. ix, p. 100, 1903. 



2 ' Ann. Sc. Nat./ 8 C ser., t. v, p. 298, 1898. 



