Oatly Marine Laboratory^ St. Andrews. 181 



in situ were brought from the banks of the Kinness Biira 

 near the harbour towards the end of May, and a strict scrutiny 

 made of the tubes and tlie mud lining them. Numerous 

 postlarval forms wei-e thus obtained, but no trace of trocho- 

 ]>hores or other early stages. Whether these stages had been 

 ])assed in sucli an environment before the examination, or 

 whetlier the later larvaj to be subsequently d ascribed had 

 .settled in the mud of the tubes after a pelagic stage is yet 

 undetermined. 



The youngest stage observed has three bristled segments 

 (PI. VITI. figs. 4 & b), 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 

 (fig. 5). 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 

 (fig. 4) . 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 (PI. VIII. 

 fig. 6). The opaque part of the gut extends over the last 

 two bristled segments. The minute bristles already present 

 the typical structure of camerated shaft and homogomph 

 articulation of the end of the shaft, and are in two bundles in 

 eacli foot. 



No younger form has yet been found amongst the mud or 

 the adults, so that it is probable that they settle down at this 

 stage. Moreover, no pelagic larvae appeared in the vessels ; 

 yet as the postlarval forms wdth three bristled segments 

 occurred in the mud of the tubes of the adult, it would appear 

 that all do not wander. 



When the postlarval form has four bristled segments 

 the head has two eyes on each side, placed close together 

 and posteriorly, a pair of short frontal tentacles, short 

 palpi which ])resent no distal articulation, a pair of tentacular 

 cirri, and two short anal cirri. Behind the head, which 

 bears the tentacular cirri, is a region with only bristles on 

 each side ; a foot with a large bristle-tuft and a minute 

 dorsal cirrus follows, and then a second foot of similar 

 structure. A rudimentary foot comes next, with a bristle- 

 tuft on one side. A rudimentary ventral cirrus occurs on 

 each foot. A pair of minute jaws having two teeth behind 

 the anterior fang is found in the proboscis. Vast swarms of 

 Infusoria (like monads) frequent the moist and odoriferous 

 nuul in which the young Nereids occur. 



The postlarval form of the 28th May (PI. VIII. fi--. 7) 



