448 NATURAL SCIENCE. Jone, 
among spiders it possesses four pairs of spinning mammille. While 
the Mygalomorphe rarely have more than two pairs, the Arachno- 
morphe always have three, and Pocock thinks that the extra central 
spinning organ (cribellum), found in some families of the latter, 
represents the fourth pair of spinners of Liphistius fused together. 
In this new classification, therefore, the archaic characters of 
Liphistius are emphasised, and it is regarded as a survival of an 
ancestral form of spider in which the abdominal segments have not 
yet become fused, and still bear the spinners on their ventral aspect. 
The animal is, to some extent, a connecting link between the spiders 
and the scorpion-spiders (Pedipalpi). Weare thus led to consider 
the relationships which exist between the various orders of the 
Arachnida—a subject also dealt with by Pocock in a later paper (2). 
His principal contention is that if arachnids are descended from 
ancestors which must have possessed a long series of nearly similar 
segments, those modern representatives of the groups in which the 
segmentation is best preserved must be the most primitive. On these 
grounds he considers the scorpions as the lowest living branch of the 
arachnid stem, in opposition to the views of Thorell and others, who 
have regarded them as the highest. There can be no doubt that 
Pocock’s opinion will meet with general acceptance among biologists. 
Deriving the arachnid orders immediately from an ancestor with 
a long abdomen of twelve segments and a telson, Pocock indicates 
the modifications which have probably occurred in each group. In 
the scorpions these segments are all present, but the hinder six are 
much reduced in bulk to form the post-abdomen, the telson being 
utilised as the sting. In the scorpion-spiders there has been a great 
reduction of the hindermost segments; the tail in Thelyphonus repre- 
sents the telson. Liphistius, with its much-shortened and partially 
segmented abdomen, connects these with the higher spiders in which 
the abdominal segments are completely fused together. Nearly 
related to the Pedipalpi, but with trachez instead of lung-sacs, are 
the Solifuge! and false-scorpions (Chelifers), with the number of 
abdominal segments complete, or but slightly reduced. On a higher 
branch of the stem bearing these come the harvestmen (Phalangida), 
with the abdominal segments generally reduced in number, and fused 
with the cephalothorax anteriorly. From these the mites (Acari), 
with the whole body fused together, must probably be regarded as a 
degraded offshoot. 
The relation of the mites to the rest of the Arachnida has been 
also recently discussed by Bernard (3), who gives reasons for believing 
that these creatures are not examples of true degradation, but that 
they have become fixed at a larval stage of development. Comparing 
their digestive, vascular, and nervous systems with those of the 
t Bernard (A. M. N. H. (6), vol. xi., 1893, pp. 28-30) has announced recently 
the discovery of a sensory organ on the pedipalp of Phrynus, similar to that on 
the homologous appendage of Galeodes. 
