310 ARACHNIDA—PEDIPALPI CHAP. 
genital opening and two pulmonary stigmata, while the other 
stigmata are behind the second ventral plate, which corresponds 
to the third abdominal segment. On the last abdominal 
segment there are often two or four light-coloured spots called 
“ommatoids,” and considered by some authors to be organs of 
sight. Laurie, however (vide infra), thinks it more probable 
that they are olfactory in function. 
The Schizonotidae (see p. 312) have a two-jointed carapace, and 
do not possess more than two eyes. There is a short unjointed 
tail-piece. 
In the Tarantulidae (Phrynidae) the whole body is much 
flattened and extended laterally, the undivided carapace being 
reniform, and broader than long. The long non-chelate pedipalps 
have their basal joints free and movable, and there are several 
sternal plates. There are nine abdominal tergal plates, the last 
three diminishing rapidly in size, and the last plate covering 
a button-like terminal portion of the abdomen. ‘The first 
abdominal ventral plate is largely developed, as in the Thely- 
phonidae, and the genital orifice and pulmonary stigmata are 
in the same situation as in that group. The Tarantulidae have 
glutinous glands in the first abdominal segment which are capable 
of spinning a few irregular threads. 
In the whole group paired circular depressions are conspicuous 
dorsally on all the abdominal segments. These indicate the 
points of attachment of the dorso-ventral muscles. 
Internal Structure.—The anatomy of the Pedipalpi has been 
very inadequately studied. Disconnected notes on various points 
of structure have been published by various morphologists, but 
no complete investigation has yet been made of the internal 
organs. This is largely due to the difficulty of obtaining 
material, and the bad state of preservation of the internal parts 
of such specimens as have been available for dissection. 
The following points have been made out in the anatomy of 
Thelyphonus.' 
The alimentary canal commences after the mouth with a 
pharynx which, though not dilated, is furnished with sucking 
muscles. It then narrows into an oesophagus which passes 
through the nerve-mass, and afterwards dilates to form the mid- 
gut, which immediately gives off two large lateral diverticula 
1 See M. Laurie in J. Linn. Soc. Zool. xxv., 1894, p. 20. 
