ON ECHINORHYNG'HUS ANTARCTICUS AND ITS ALLIES. 



41 



This layer is very dense. The last layer is comparatively thin, 

 embryos were hooks observed (fig. 8). 



Testes. 



Upon none of the 



These are large, and consist of two pairs. The members of a pair are closely 

 apposed to each other, but are easily separated by the dissecting needle, and, further, 

 are seen in sections to be quite distinct. They lie antero-posteriorly ; the anterior 

 member is pear-shaped, the posterior is more ovoid. Attached to the anterior end of 

 each pair is a soft spongy-looking gland, whose exact nature is undetermined. It has 

 no connection with the cement glands, which lie posteriorly. 



Lemnisci. 

 These consist of a pair of fairly broad bands, in which no canals could be observed. 



FIG. 2. E. piriformis. 



FIG. 3. E. hystrix. 



FIG. 4. E. antarcticus. 



The present form appears to be new to science, and it has been named Echino- 

 rhynchus antarcticus, n. sp. Its distinctive features are, specially, the form of the body 

 and the distribution of spines upon it ; the size and shape of its rostrum, and the size, 

 form, and number of its hooks ; the characters of the sub-cuticle ; the arrangement and 

 distribution of the lacunae ; the relative sizes of the sexes ; the size of the shelled 

 embryos, and the number of the testes. Of the foregoing, the form of body and dis- 

 tribution of spines upon it are more especially adaptations, as already suggested, for more 

 secure fixation upon the host ; and possibly, in the case of the male, which shows some 

 degree of flattening, in addition the spines upon this flattened area are of service in 

 locomotion. These features are readily understood as modifications (acquired by 

 natural selection) of a symmetrical type with uniformly distributed spines. Different 

 modifications of such a type are not wanting, and an interesting series exists in 

 E. striatus, E. hystrix, E. piriformis, E. antarcticus. The distinctive features of these 



(ROY. soc. OF EDIN. PBOC., VOL. xxvi., PP. 441-442.) 



