682 MR JAMES MURRAY ON 
moulting, there was a considerable elongation of all the dorsal and lateral processes, as 
well as development of the fringe and of the barbs of the outer claws. Many observa- 
tions of a species, common in Loch Morar, and which I[ regard as belonging to 
FE. granulatus, are instructive as bearing on the value of all those points as specific 
characters (Plate II. figs. 6a to 67). The larva was not certainly seen, but many 
moults of large animals were observed. The youngest individuals seen had four claws, 
without barbs on the outer ones; the fringe consisting of short blunt processes standing 
far apart ; the dorsal processes being a large spine on the first pair of plates, a short spine 
on the second pair, and a mere knob on the lumbar plate ; the lateral setze were ¢ and 
d (RicHTERS). 
In a single moult the large dorsal spine elongated till it might be called a seta, the 
short dorsal spine became a long one, the knob became a spine, the fringe acquired long 
teeth standing close together, straight barbs appeared on the outer claws of the last legs, 
and the lateral setae elongated. In the last stage seen there were two pairs of dorsal 
setee, the first very long; the lateral setze were also very long; the outer claws of all 
the legs had straight barbs, and those of the last legs had three such barbs. 
Although no new processes appeared during these moults, except the barbs of the 
outer claws, the changes are sufficiently great to render imperative extreme caution in 
separating species by any of those characters, even if sexually mature individuals are 
seen. We may fully expect that the working out of the life histories would lead to the 
union of several of the earlier described species, and perhaps of some of the later ones 
as well. 
Species.—All observers have agreed in basing their species chiefly upon the number 
and position of the spines or other processes; but it now begins to be suspected that 
this may carry us too far, and give us a multitude of species founded upon larval forms. 
RicHTErs advises that no species be described unless the eges have been seen, or there is 
some very marked peculiarity. Now that it is known that some species lay eggs when 
not nearly full grown, even this rule may not be a perfect safeguard. It is a safe rule 
that no form should be separated from a known species merely because of one pair of 
spines more or less, or a difference in size of these appendages, unless there are other 
characters, whether of texture, claws, fringe, or what not, to support it. Another rule, 
laid down by JENNrNGs (7) in regard to Rotifera, might well be applied to Tardigrada, 
viz., that no species should be described without an accompanying figure. JENNINGS’ 
remark, that in most instances the description could be better dispensed with than the 
figure, applies equally to all microscopic biology. 
Echiniscus arctomys—Eur. (4), (5), (9). 
Specific Characters.—Small; nine minutely punctate dorsal plates. No setee or 
spines except the six invariably present on the head. ~ Legs slender, no fringe on last 
pair; all claws without barbs. 
