308 MR. F. E. BEDDARD ON NEW OR [May 18, 



5. Remarks on the Variation of Perionyx excavatus, 

 E. Perrier. 



Hardly anything is at present known with respect to the varia- 

 tions in structure which may occur in a given species of Earthworm ; 

 and in order clearly to define the limits of different species it is 

 evidently a matter of some importance to ascertain how far variation 

 may take place. The description of by far the majority of exotic 

 forms of Lumbricidee has depended upon the dissection of a very 

 few examples, so that many of these descriptions must be qualified 

 by admitting the possibility that they relate only to what may be 

 termed for convenience' sake the normal conditions of structure. 

 Such a criticism, however, can only be applied to those instances in 

 which a species or genus has been created for the reception of a 

 single individual, which may show well-marked divergencies in 

 structure from its immediate allies ; if a number of individuals agree 

 to differ from a second series of individuals in certain well-marked 

 characters, it would be obviously necessary to separate the two 

 groups either generically or specifically as the case demands. 



The Lumbricidae are a group which exhibit a most remarkable 

 variability in internal structure, more especially of the generative 

 system ; in accordance with this variability they have been divided 

 into a considerable number of species and genera. It might well be 

 expected that this group, which is apparently universally distributed 

 and is at present no doubt as abundant, or even more abundant', in 

 individuals as well as in species as it ever was, is still in course of 

 differentiation into new forms ; any accidental variation may be the 

 first term of a series which will ultimately lead to the formation of a 

 new species. 



I have had the opportimity of examining, through the kindness or 

 my friend Mr. Herbert Barwell, rather more than 'lOO individuals 

 of a Philippine Earthworm belonging to the genus Perionyx ; this 

 worm exhibits a number of variations which appear to me to be 

 really variations, and not marks of specific distinctness. The reasons 

 for this belief will be stated after the facts liave been detailed. 



The Earthworm in question appears to be identical in every respect 

 with Perio7iyx excavatus: it differs in no point from M. Perrier's^ 

 description of that species. I need hardly therefore describe in 

 detail its specific characters, as it would be merely repeating what 

 Perrier has already said ; it will be necessary, however, briefly to 

 indicate the main features of its organization in order to render 

 clear what follows. 



The setae are disposed in a continuous row round the middle 

 of each segment ; they are not disposed upon a ridge as in Perickceta, 



^ There seems to be a certain relation between the abundance of Earthwoi-ms 

 and the cultivation of the soil ; this fact is noted in a short article on Eartli- 

 •vvornis in the ' Field' of March 27, 1886. My friend Mr. James Cavan informs 

 me that in California fishermen know well that if worms are required for bait 

 they must be sought for in cultivated land. 



- NouT. Arch. d. Mas. t. viii. (1872) p. 126. 



