Nos. IAND2.] COTYLASPIS INSIGNIS. 23 



nucleus (see Fig. 28), but have not been able to determine whether 

 it really belong-s to the eye or is merely one of the parenchyma 

 nuclei accidentally so located. In other eyes the pigment is not so 

 clearly arranged in the form of a cup, and yet the globular shape 

 is retained, and in still other cases the pigment is shapeless. 



These eyes and their degeneration are facts that must be inter- 

 preted in connection with any conception of the biological relations 

 of Cotylaspis which ,we may adopt. Leidy explained them by 

 correlating them with the ectoparasitic habit of the worm. But 

 this interpretation is weakened by the fact that they degenerate 

 in the anodon, and we are consequently forced to look for another. 

 It is more plausible it seems to me to regard the degeneration of the 

 eyes as an indication of a previous habit in which they were useful, 

 such as a free life, or to fall back on phylogeny and explain them 

 by recency of the derivation of Cotylaspis from free ancestral 

 forms, such as the turbellarians. In favor of the latter interpre- 

 tation is the somewhat generally accepted belief that the Aspido- 

 bothridae are a very primitive trematode family, and this view is 

 not incompatible with the other, that of a free existence prior to the 

 occupation of the anodon. 



Sections which cut the animal tangentially give surface views 

 of the cuticle and show structures imbedded in it which appear 

 to be nervous, and perhaps tactile. Their location can be seen 

 by a reference to Fig. 30. They are not regularly arranged and 

 are more numerous at the anterior end of the worm. A section 

 shows them to be located entirely in the outer portion of the cuticle 

 (Fig. 31), and in some cases a distinct conical elevation of the 

 cuticle surrounds the outer part of the organ. It consists of an 

 oval, homogeneous, solid, central portion occupying a space which 

 is supplied in its .wall with several stainable threads of granular 

 substance, all arising from a common center at the base. These 

 threads are seen in surface views as a ring of minute points (Fig. 

 30), and have every appearance of being nervous. At the base of 

 this structure a single stronger thread passes through the remain- 

 ing portion of the cuticle and is lost in the parenchyma. I regard 

 is as the nerve, though I have not been able to connect it in any case 

 with an undoubted member of the nervous system. Sense organs 

 in the cuticle have been reported by Blochmann '95, certain of 



