THE ANATOMY OF SOALTBREGMA INFf-ATUM. 245 



At each side of the prostorainm there is a uai'row longi- 

 tudinal slit (fig". 3), which leads downwards, backwards, and 

 inwards into the nuchal organ (for description see p. 269). 



There are small structures on the body-wall situated in 

 each segment about midway between the notopodium and 

 neuropodium. At first sight they are liable to be mistaken 

 for apertures, and Levinsen (1883, p. 133) suggested that 

 they were sexual openings. On further examination each of 

 these proves to be a depression, from the floor of which a 

 small elevation arises, the apex of which may be seen a little 

 below the level of the mouth of the pit (figs. 1, 4, 5, ^S*. 0.). 

 These structures are best seen in the segments just behind 

 the branchial region, but on careful examination they may 

 be seen in all the chastigerous segments of the animal. 

 Sections prove that these are lateral sense organs, similar to 

 the '^ Seitenorgane " described by Eisig (1887) in the Capi- 

 tellidae. A detailed description may be found on p. 270. 



Size. 

 Scalibregma inflatum varies in size between wide 

 limits. Of the twenty-two complete specimens in my posses- 

 sion the smallest is 5 mm. long, and the largest 56 mm. long 

 and 10 mm. broad at its widest part. The latter is one of 

 the largest specimens yet recoi-ded (fig. 1). Sars's specimen 

 was 58'5 mm. long and 5 mm. broad at its widest part ; and 

 Rathke^s example was one inch and seven lines (about 40 mm.) 

 long and 5 mm. broad. In the specimen 56 mm. long there 

 are sixty-one segments, and a very short pygidium (about 

 •3 mm. long). Parapodia are clearly visible on the first fifty- 

 three segments, but those of the succeeding segments are 

 very small, or absent altogether. It is interesting to note 

 that in Sars's specimen there are also sixty to sixty-one seg- 

 ments. One of my specimens 35 mm. long contains ova which 

 appear to be almost ripe, so that the animal reaches maturity 

 when little more than half its maximum size. 



Colour. 

 Sars has recorded the colour of his living specimen. The 



