290 SYNOPTIC COLLECTION. 



the body the bristles or setae are distinctly seen (fig. i), 

 but it is not definitely known whether these worms pos- 

 sessed locomotive paddles called parapodia. The jaws 

 are found in place (fig. i) and in some species of 

 Eunicites (E. dentatus, fig. 3) they bear prominent teeth, 

 reminding one of the toothed jaws of the Palaeozoic 

 species, Eunicites simplex H. (PL 724, fig. i) and E. 

 clintonensis H. (fig. 2). 



Doubtless naked worms with primitive structural fea- 

 tures exist or have existed in the abyssmal depths of the 

 sea, but these could hardly be brought to the surface in 

 perfect condition. Most of the worms so far obtained 

 have been protected by a tube, and are specialized by 

 the possession of numerous organs. There is evidence, 

 furthermore, that many of these forms have migrated 

 from shallow water to the deep sea, and therefore they 

 possess a combination of adaptive characters which ren- 

 ders them puzzling and of little phylogenetic value. 



In default of fossils representing pre-Cambrian or 

 Cambrian fleshy forms, and of primitive deep-sea species, 

 we should naturally turn, as we have done already in sev- 

 eral groups under similar circumstances, to the embry- 

 onic and larval stages of development of a primitive, 

 marine, and free-swimming member of the class under 

 consideration. 



There are many reasons for considering Dinophilus as 

 a primitive worm, although its development has not been 

 worked out in detail nor the trochophore (if one exists) 

 figured, yet the young stage (PI. 726, fig. i, D. taeniatus) 

 is little more than a trochophore. There is no meta- 

 morphosis, and it does not appear that the larval stages 

 peculiar to those forms that pass through a metamorpho- 

 sis are skipped in the development of this worm. We 

 should say, on the contrary, that these stages have never 

 occurred in the ancestors of Dinophilus and that the 

 embryo develops gradually from the egg to the young 

 form (fig. i). In this stage the body is transparent, and 



