ON ECHINORHYNCHUS ANTARCTIUUS AND ITS ALLIES. 39 



Length of 12 Males L th of 32 Femalea examined, 



examined. 



mm. 



5-25 



4-20 



5-20 



4-20 



4-10 



5-00 



4-00 



3-80 



4-30 



4-75 



4-5 



4-2 



The average length for males examined is 4 '46 mm., whilst for females the figure 

 is 3 "73 mm. The measurements were taken from the tip of the body to the farther 

 margin of the disc. In the males the posterior region is flattened upon the spine- 

 bearing surface, and slightly keeled along the sides. The tip is usually curved upward ; 

 the genital opening is not quite terminal, and there is no marked cleft. In the female 

 the body is expanded around the genital aperture, which is situated at the base of a 

 well-marked cleft. This cleft is upon the lower or naked side of the body. 



As regards proportions of the sexes, it was noted that of 60 specimens found, 15 

 proved males and 45 females. 



Body-wall. 



There is a well-developed cuticle and sub-cuticle. The latter contains both longi- 

 tudinal and circular fibriUse in which the spines are embedded, and a hypodermis, in 

 which are situated oval-shaped nuclei. The sub-cuticle in the region devoid of spines 

 is thicker than in any other part of the body, and here, for the most part, are to be 

 found the sub-cuticular lacunae. These consist of a system of very much branched 

 canals, which interlace. They were not observed within the disc-like portion of the 

 anterior region (fig. 4). The hypodermis shows a limiting membrane, against which is 

 placed the musculature of the body-wall, arranged in closely set rows. The cells are 

 nematoid in type ; in cross section they exhibit a U-shaped contractile portion, and a 

 larger non-contractile part in which the nucleus lies. In most cases a single U-shaped 

 part corresponds to a single cell, but cases were observed, usually occurring in groups, 

 where as many as three or four appeared to possess a common non- con tractile part 

 forming relatively a giant type of circular muscle cell. The longitudinal muscles are 

 fewer, and here the contractile part encloses the non-contractile in a sheath-like 

 manner. 



(ROY. soc. OF EDIN. PROC., VOL. xxvi., pp. 439-440.) 



