Pycnogonid(X 



115 



other excrescences of tlie stem or leaves, but a nuinhei' of Table-case 

 species are wandering forms, or live in the galls of other species. -^'^- ^^'• 



A drawing of one of these mites (Eriophi/cs silvicola), which 

 produces galls on the leaves of the stone-bramble (Btibiis saxaiilis), 

 is placed in Table-case 26, and models of some of the commoner 

 galls, and enlarged sketches of the mites which cause them, are 

 sliown along tlie wall to the left of the Case. Drawings of the 

 black-currant mite [Eriophz/rs rihis) and of the plum mite 

 (Eriophijes j)nini), together with specimens of the plants they 

 infest, showing tlie damage wdiich they cause, are shown in the 

 North Hall. 



Sub-class 2.- PYCNOGONIDA. 



The Pycnogonida, Pantopoda, or Podosoniata, are a small group 

 of marine animals, here treated as a sub-class of tlie Arachnida, 



Diagram of a Pycnogonid, Nympkon {Boreonymphon) robitsfn»i. 

 Enlarged. [Table-case No. 26.J 



although it should be mentioned that many zoologists refuse to 

 admit tbat tliey liave any close affinity w^ith that group of animals. 

 The body (Fig- 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. Four 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.) aie sensory palps, 

 placed at the sides of the proboscis; the third pair (in.), placed 



I '2 



