Pycnogonida. 
115 
other excrescences of the stem or leaves, but a number of Table-case 
species are wandering forms, or live in the galls of other species. No - 26, 
A drawing of one of these mites ( Eriophyes silvicola), which 
produces galls on the leaves of the stone-bramble (JRubus saxatilis), 
is placed in Table-case 26, and models of some of the commoner 
galls, and enlarged sketches of the mites which cause them, are 
shown along the wall to the left of the Case. Drawings of the 
black-currant mite ( Eriophyes ribis) and of the plum mite 
( Eriophyes pruni), together with specimens of the plants they 
infest, showing the damage which they cause, are shown in the 
North Hall. 
Sub-class 2. PYCNOGONIDA. 
The Pycnogonida, Pantopoda, or Podosomata, are a small group 
of marine animals, here treated as a sub-class of the Arachnida, 
Diagram of a Pycnogonid, Nymphon ( Boreonymphon ) robustum. 
Enlarged. [Table-case No. 26.] 
although it should be mentioned that many zoologists refuse to 
admit that they have any close affinity with that group of animals. 
The body (Pig. 78) consists, as a rule, of a head-segment, 
followed by three free somites and a small terminal lobe repre- 
senting the abdomen or opisthosoma. Pour pairs of very long 
legs (iv.-vii.) are attached, the first to the head-segment, and the 
others to the three free somites. In addition, the head-segment 
may bear three pairs of appendages ; the first pair (i.) are chelate 
(or pincer-like), and overhang a tubular proboscis on which is the 
opening of the mouth ; the second pair (ii.) are sensory palps, 
placed at the sides of the proboscis ; the third pair (hi.), placed 
