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the upper reservoir on lower Hampstead Heath to those 
readers who wish to get abundance of both Cheetogaster 
Limned and Cheetogaster diaphanus. 
Classification. — In vol. xxvi of the ‘ Linntean Transactions,’ 
p. 744, speaking of the zoological position of Chaetogaster, I 
remarked, in reference to the genera Chaetogaster, Parthe- 
nope, 1 Thysanoplea, and JEolosoma, “ they are now put 
with the Naids, from which certainly Chaetogaster differs as 
much as Nais does from Lumbricus.” 2 The classification 
here indicated has been since advocated by M. Leon Vaillant 
in his interesting paper already alluded to (‘Ann. des Sciences 
Naturelles,’ 1868). M. Vaillant proposes, as primary groups 
of Oligochaeta, these, viz. Lumbricina, Naidina, and Chaeto- 
gastrina. The limitation of Lumbricina given by M. Vaillant 
is, perhaps, not quite what could be wished, his Naidina and 
Lumbricina forming more naturally four, or at least three, fami- 
lies; but I believe the family Chaetogastrina to be well justified. 
M. Vaillant places in it Chaetogaster and Ctenodrilus (Parthe- 
nope) . It is this Parthenope which made me hesitate to propose 
a family for Chaetogaster ; for it has not the specialised cephalic 
fasciculi of Chaetogaster (Schmarda’s Chaetogaster from South 
America seems also to be in this case, and further agrees with 
Parthenope in its having only three bristles in a fascicle), 
and thus seems to bridge over the chasm to Naidina, its 
ciliated prostomium and spotted integument also helping on 
the way through CEolosoma. Nevertheless, its uncinate bris- 
tles in single series and neural position, and its general form, 
agree with Chaetogaster. We cannot hope or reasonably 
expect that throughout the organic w r orld Nature should 
destroy some forms and keep others going, precisely in such 
a way that those at present existing may form genera, fami- 
lies, orders, or classes at all comparable to one another in 
size or significance. A finer scale for indicating the gaps 
between various groups is now needed than any suited to the 
philosophy which regarded species and classes as divine 
institutions, but allowed men to speculate as to the less sacred 
“ families” and “ orders.” In the assemblage of forms known 
as Vermes this fact is strikingly exemplified ; and in the con- 
struction of the genetic tree of that group Chaetogaster will 
1 This is Schmidt's genus ; it is identical with Claparede’s Ctenodrilus, 
a fact which M. Vaillant appears to have overlooked. In PI. XV, fig. 9, I 
have eiven a sketch of the worm. 
2 “The pap between Nais and Chaetogaster is not so great as I thought 
when writing as above. The great difference is in the suppression of fas- 
ciculi in the pharyngeal region of Chaetogaster. In other matters they are 
closely allied, e.g. genitalia, form of satae, vascular system, &c.” 
VOL. IX. NEW SER. 
T 
