Miscellaneous. 325 



I shall describe in more detail the anatomy of this interesting 

 type ; but I wish to dwell at present upon the affinities which it 

 presents to an important family of the Chaetopoda, the Opheliidae, 

 affinities already foreseen by M'Intosh, and winch appear to me 

 to be at least as great as those of the Polygordians with Saccocirrus, 

 put forward by Uljaniu. 



The type Polygordius is not, as has been said, an intermediate 

 type of worm ; it is an archaic and aberrant type of Annelid. 



Polygordius is not a type intermediate between the Annelids and 

 the Nematodes. The resemblance to the Nematodes consists solely 

 in the general arrangement of the musculature, and especially in 

 the excessive development of the longitudinal muscular lamellae, 

 from which result a very peculiar habit and a characteristic mode 

 of progression. But the same arrangement exists in certain Anne- 

 lids {Polyophthahrms), the movements of which are modified in a 

 similar way ; it is a character due to a convergence easily explained 

 by adaptation to special surroundings. 



Nor is Polyyordins an intermediate type between the Annelids 

 and the Nemcrtians, the relationship of which to the Gymnotoca 

 appears to me exceedingly problematical. The vibratile cephalic 

 pits of the Polygordians are by no means comparable to those of the 

 Nemertians. Similar vibratile organs, fixed or exsertile, exist 

 in Annelids belonging to the most various families, such as 

 Staurocephalus Ghiajii, Clap., Pcedophylaas veruger, Clap., Syllis 

 simillima, Clap., Arhcia (Erstedtii, Clap., Ctenodrilus pardalis, Ciap., 

 Ammotrypane aidogaster, Rathke, Ophelia, &c. 



The absence of external vibratile cilia in the Polygordians, of 

 which the digestive tube is ciliated internally throughout its whole 

 length, is explained by the thickening of the cuticle and the great 

 development of the musculature. The cuticle of L. erythrophihalma 

 bears from place to place traces of ciliary tufts analogous to those of 

 Polgophthalmus ; and I should not be at all surprised if we were to 

 find among the Polygordians types strongly ciliated externally. 

 The Staurocephalidre, the embryonal form of which is not without 

 analogy with the Polygordians, present a complete ciliary covering 

 in certain species (Prionognathus ciliatus, Keferstein). 



The absence of setae in a Clmetopod need not surprise us more 

 than the absence of articulated limbs in certain Arthropods (Saccu- 

 lina, Cryptoniscus, &c). We may trace the gradual disappearance of 

 these organs in the series of the Opheliidae, from Ophelia to Polg- 

 ophthalmus and Ammotrypane, certain species of which, described 

 by M'Intosh, are almost certainly destitute of setae. 



The organization of the PolyopJithalmi scarcely differs from that 

 of Idmnotrypane. At Concarneau I studied a large Polyophtludmus 

 (0*3 metre and more) common among the Corallines and Melo- 

 besice, which I identify provisionally with P. pictus, Dujardin. The 

 form of the mouth, the vibratile apparatus, the appendage of the 

 pharynx, the anal papillae, the ventral furrow, and the general 

 arrangement of the musculature perfectly remind one of what exists 

 in Linmotrypane. The resemblance is still greater if we compare 

 two transverse sections suitably chosen. 



In Saccocirrus the arrangement of the muscles and especially that 

 Ann. & Mag. N. Hist. Ser. 5. Vol. vi. 23 



