320 



NEREIS DIVERSICOLOB, 



seawards. There is no doubt, however, that, without change in the condition of the feet 

 and bristles, the species is an apt swimmer, progressing through the water swiftly in 

 graceful screw-coils. 



Towards the end of May (29th) and for some time previously signs of degeneration 

 appear in certain ova, as if they were in process of absorption. These ova are smaller, 

 minutely granular, and with larger oil-globules. The larger ova have lost the germinal 

 vesicle and spot, and transmit light more readily than formerly. Nothing is seen to 

 suggest the view that certain ova are undergoing development, for, when kept in vessels 

 both of sea- water and fresh water, they are rapidly disintegrated. 



Some females at this elate have shed all their ova, and are of a pale brownish-yellow 

 colour, occasionally with a minute dusting of yellow grains along the dorsum. 



Having failed to secure the early larvae by any of the methods alluded to, masses of 

 the clayey mud with the adults in situ were brought from the banks of the Kinness 



Fig. 72.— Maxilla of 

 larval N. diversicolor. 



Fig. 71. — Post-larval Nereis diversicolor 

 with three pairs of bristles. 



Fig. 73. — Post-larval N. diversicolor 

 with five pairs of bristled feet. 



Burn near the harbour towards the end of May, and a strict scrutiny was made of the tubes 

 and the mud lining them. Numerous post-larval forms were thus obtained, but no trace 

 of trochophores or other early stages. Whether these stages had been passed in such an 

 environment before the examination, or whether the later larvae to be subsequently 

 described had settled in the mud of the tubes after a pelagic stage, is yet undetermined. 

 The youngest stage observed has three bristled segments (Fig. 71), a head with two 

 short palpi, and two short frontal tentacles. The eyes are imperfectly differentiated, 

 consisting of an irregular group of black pigment-granules. A tentacular cirrus 

 occurs on each side opposite the eyes. The three feet are nearly alike, each with a 

 bristle-tuft and a small dorsal cirrus, or the first is rudimentary. A minute caudal 

 cirrus is at each side of the posterior end. Between the last foot and the pygidium is 

 a projection, indicating a segment. The proboscis has a pair of jaws each with three 

 long teeth, including the anterior fang (Fig. 72). The opaque part of the gnt extends 

 over the last two bristled segments. The minute bristles already present the typical 



