OPILIONES. 547 
intromittent organ has ever been specialized, but its function assumed by the speciali- 
zation of the second pair of appendages (the palpi) in the former case, in the Opiliones 
there is a well-developed intromittent male organ or “penis” corresponding with an 
homologous organ in the female, called the ovipositor. These organs lie beneath the 
first two opisthosomatic segments, which have migrated forwards towards the region 
of the mouth (very far forward in the Plagiostethi, less so in Mecostethi), crowding the 
coxal segments of the legs together and reducing the sternal sclerites to quite attenuate 
proportions. 
The dorsal segments of the prosoma, constituting the so-called “carapace,” are 
entirely fused and bear a pair of eyes, usually placed on a larger or smaller median 
tubercle. The first five dorsal segments of the opisthosoma are also completely fused, 
but the grooves marking the original divisions are distinctly traceable in very many 
Opiliones; while the last four segments are quite separate or free, united along their 
margins by connective tissue. 
In the ventral aspect the “ prosoma” is represented by the chelz, palpi, and four 
ambulatory appendages, with the maxille and more or less obliterate sternal elements ; 
the “‘opisthosoma” by the two genital segments, the segment bearing the spiracles, 
and the six free segments, the two terminals being, however, fused together. 
The first pair of appendages are chelate for purposes of seizing and crushing prey, 
and. in the males of many forms they are enormously developed. The second pair 
constitute the so-called ‘‘ palpi,” and usually terminate in a strong single claw. They 
are variously armed with formidable spines, and in such cases are used for the com- 
pression of the prey against the mandibles and maxille in the operation of mastication. 
The third pair of appendages are ambulatory in their function, constituting the first 
pair of legs. ‘The fourth pair, usually considerably lengthened and slender, are in 
many cases further specialized, and the terminal segments are broken up into numerous 
small sections. They have ceased to be purely ambulatory, but have become used for 
tactile purposes, their function being analogous to that of the third pair of appendages 
in the Pedipalpi, most noticeable amongst the Phrynide. The fifth and sixth pairs are 
used for ambulatory purposes, while amongst the Cosmetide and Gonyleptide, for 
instance, the sixth pair is often in the male sex highly developed and armed with 
specialized spines, chiefly on the femoral segment. 
It is as yet by no means clear what the exact use of these specialized posterior 
legs in the male sex may be, though possibly they serve as claspers in the act of 
copulation. 
The tarsal claws vary in number in the different families, and have been utilized as 
a basis of the highest importance for the division of the Opiliones into three suborders 
by Loman. 
For the present, however, the view adopted here is that recently put forward by 
Mr. R. I. Pocock, that the character of the sternal sclerites, with others of considerable 
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