The President's Address. By A. D. Michael. 19 
is a very curious one, for it is not chelate like the pedipalps of the 
Scorpionidse, or a lobster’s claw, and yet there is an apparatus which 
is almost a chela. The penultimate joint of the palpus is carried 
nearly straight to its termination, or curves inward in a more or lees 
clawlike form, hut before its distal end the terminal joint is articulated 
on ; it has free motion but is not a claw ; it is usually a soft pyriform 
piece articulated by its smaller end ; and between this and the often 
soft rodlike penultimate joint the prey is held ; yet it is retained very 
efficiently. The small group of the Cheyletidm is closely allied to 
the Trombidiidm, although distinguished from them by some very 
striking features ; it is here that the raptorial palpus attains its 
greatest development among A carina. In such a species as Cheyletus 
jlabellifer the thickness of the palpi, as compared with that of the 
whole rostrum, is surprising ; each palpus curves inward, and usually 
terminates in a simple, fixed, claw-like process of hard chitin ; the 
victim is held between the two palpi ; so far the holding between the 
rtwo palpi and the great size of the organs are the only remarkable 
features ; but the really singular character is the presence of four or 
five long rods of clear chitin movably articulated to the inner side 
of the palpus, each rod armed with a series of strong spines or 
pectinations on its inner, or when in action its hinder side ; these 
spine-bearing rods all differ from one another, and probably they 
serve to prevent the escape of a victim. There is no hope of release 
for the unhappy Acarid or Thysanurid once seized by the palpi of 
the Cheyletus ; for in spite of the small size, less than the fortieth of 
an inch in extreme length, there probably is not a more ferocious 
creature upon earth than this minute, soft-bodied, white Acarus. It 
is blind, and only detects its victim by keeping its slender fore-legs, 
with long tactile hairs at their ends, constantly trembling in the air 
before it ; but this means of information is so accurate and sensitive 
that the Cheyletus springs upon its prey with a bound like a micro- 
scopic tiger before one would have thought it possible for the tactile 
hairs to have touched it. So extraordinary does this appear to the 
observer that I have often wondered whether some other sense, such 
as smell, may be concerned in it, but we have not any grounds for 
asserting that this is the case. Until it makes its bound the Cheyletus 
usually seems as inert a creature as a tree-frog does before it suddenly 
springs at a fly ; and yet it must possess remarkable powers of loco- 
motion, for it has a knack of turning up everywhere, even in places 
which have only been exposed for a very short time, which is most 
deceptive, and has led to many errors ; thus an eminent English 
biologist described it as inhabiting the depths of the sea, having found 
it on his dredge almost immediately it came out of water ; and an 
equally eminent French entomologist described it as parasitic on the 
human brain, having found it on the brain immediately after the skull 
had been opened in one of the Paris hospitals. 
The anchoring-palpus is closely allied to the raptorial, and indeed 
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