SABELLIFORMIA 



337 



which is frequently notched, so that a lateral and a ventral lobe 

 on each side may be distinguished (Fig. 133, B, p. 261). The 

 thorax consists of nine segments, and is provided with ventral 

 " gland shields," which are continued along; the abdomen, where 

 they are subdivided into two by a ciliated "faecal groove," which 

 sometimes bends to one side on reaching the thorax, and may 

 extend forwards along the dorsal surface to the head: this groove 

 serves to carry the faeces out of the tube. The gill filaments 

 are always provided with secondary processes, and may be pro- 

 vided with compound eyes. 1 The tubes of the Sabellidae are 

 always of fine mud or of sand. 



Sabella pavonia Sav. is about 10 to 12 inches long and 

 about ^ inch across ; the tube of fine mud is considerably longer 

 and embedded deeply in the mud, with its free end projecting to 

 some 2 or more inches, where it serves for the attachment of 

 seaweed, Polyzoa, Hydrozoa, etc. The colour of the animal is 

 orange-brown ; the gills, which are about 1^ inches long, are 

 green (due to contained blood) marked with more or less extensive 

 brown or purple-brown spots, which may even hide the green 

 tint. There is a pair of dark filaments arising between the 

 dorsalmost gill filaments, 

 which have been errone- 

 ously regarded as " pro- 

 stomial tentacles " ; they 

 are, in fact, prolongations 

 of a peculiar membrane or 

 lip round the base of the 

 gills, which bounds a groove 

 leading to the mouth. 

 These lip -processes (Fig. 

 133, B, /) occur in other 

 Sabellids. Atlantic, North 

 Sea, and Mediterranean. 



Branchiomma vesicu- 



losum Mont, forms a sandy Fig. 182. A, A gill filament of Branchiomma ; 

 . , , .., , B, of Dasychone. a, Axis ; /, secondary flla- 



tube near low tide -mark. me nts ; o, eye j *, dorsal appendices. 



The animal, measuring 6-7 



inches, is rich brown, darker anteriorly, abundantly speckled with 



white ; the ventral surface is pink ; the gills are green or olive- 



1 Andrews, Journ. Morph. v. 1891, p. 271. 



VOL. II 



