412 Mr. G. E. Dobson on 



LIII. — Note on Pteiygodermatites Macdonaldii, the Type of a 

 new Order of Vermes. By G. E. Dobson, M.A., M.B., &c. 



In the preceding paper Dr. Maedonald has very fully described 

 the interesting parasitic worm discovered by me in the intes- 

 tinal canal of Mega derma frons, and of which I have given a 

 short account in ' Nature ' (vol. xxii. no. 573). He has con- 

 clusively shown that tills form, though Annelidan in external 

 characters, is really to be classed rather with the Nematoid 

 worms. In assigning it then a place in the zoological series 

 we display another instance of what Dr. Maedonald calls 

 " representative relationships " — not unexpectedly, however, as 

 the following extract from one of his lately published papers * 

 shows : — 



" If we look upon the Trematoda as representing the Hiru- 

 dinei, coupling also the Oh'goeiucta with the Polycliceta, and 

 the Rotifera with the Arttculata, Prof, Huxley's interesting 

 classification, embodying a large proportion of the results just 

 alluded to, would seem to sanction the idea. Thus the cor- 

 responding part of his Table may be arranged, without mate- 

 rial change, in the following manner : — 



1. Ar.CHiEOSTOMATA. 2. Deuterostomata. 



Trematoda Hirudinei 



OUf/ocha'ta I'oh/chceta 



Jiotifera Arthropoda 



" There is surely something more than coincidence in this. 

 There may be misgivings as to the position of the Oli- 

 goch&ta] but, perhaps, something will soon turn up to recon- 

 cile it." 



This prophecy appears to be fulfilled by the discovery of 

 the parasitic worm above described, which may be considered 

 the type of a new order — Metabdellada — of Vermes f. If 

 now we seek to assign this order a position in the above 

 Table, it •will be found to fall very naturally into the position 

 previously doubtfully occupied by Oligocholia, while the latter 



* "On anew Genus of Trematoda, and some new or little-known Para- 

 sitic Hirudinei" Trans. Linn. Soc., 2nd ser. Zoology, vol. i. p. 209. 



t AVhile these notes were passing through the press Prof. F. Jeffrey 

 Bell called my attention to a paper by Dr. Wedl in Sitzungsb. Akad. 

 Wissensch. Wien, vol. xliv. p. 464, Taf. ii. figs. 5-11, in which a worm 

 (Pteryf/odermatites pkigiostoma) (not noticed in the ' Compendium of 

 Helminthology ') from the intestine of Erinaceus auritus, evidently he- 

 longing to the same genus as this parasite of Megaderma frons, is de- 

 scribed, but which may be at once distinguished from it specifically on 

 comparison. 



