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 Lumbricidz 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 Lumbricidz 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 opportunity of examining, through the kindness ot 
my friend Mr. Herbert Barwell, rather more than 400 individuals 
of a Philippine Earthworm belonging to the genus Perzonyz ; 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 have been detailed. 
The Earthworm in question appears to be identical in every respect 
with Perionyx 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 setz are disposed in a continuous row round the middle 
ofeach segment ; they are not dispesed upon a ridgeas in Pericheta, 
1 There seems to be a certain relation between the abundance of Earthworms 
and the cultivation of the soil; this fact is noted in a short article on Earth- 
worms 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. 
* Nouy. Arch. d. Mus. t. viii. (1872) p. 126. 
