462 TEANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



In many cases it was a deep crescent, the horns barely 

 touchmg the anterior pair of eyes and the convex posterior 

 margin extending to about halfway between them and 

 the posterior pair. This variety appears to correspond to 

 Hubrecht's species T. coronatum. In others again an 

 oblong band of pigment extended quite across the head 

 (almost reaching its lateral margins) immediately behind 

 the anterior pair of eyes and covering one-half to two- 

 thirds of the space betw^een them and the posterior pair. 

 This seems to be Hubrecht's typical T. melanoceplialum. 

 With respect to these two forms, however, my experience 

 both at Port Erin and elsewhere coincides with that of 

 Eiches, a complete series of intermediate varieties making 

 it impossible to regard them as more than slightly divergent 

 members of one variable species. 



This opinion was at one time held by Joubin too, but 

 in his later work (5) T. coronatum is separated from T. 

 melanocephalum and united with T. diadema, Hubrecht. 

 No Nemertine exactly agreeing with the latter has been 

 met with by myself, but the Nemertine from the coralline 

 zone described under the head of T. candidum seems to 

 come very near it. That form, however, did not show 

 any tendency to vary in the direction of T. melanocephalum 

 so far as my observations went. 



A character given for the present species by M'Intosh : 

 " Marginal stylets-sacs placed considerably in front of the 

 central apparatus" — has been repeated by other authors, 

 though to what extent this point has been confirmed by 

 their own observations does not appear. I have examined 

 the stylet apparatus in many individuals and have so far 

 failed to find a single case exhibiting this character, or 

 any difference in this respect between T. melanoceplialum 

 and its allies. 

 ■ A Nemertine having the form and general appearance 



