BOOK THIRTEENTH. 
ARACHNOIDAE. 
CLASSIFICATION. 
§ 295. 
Taz ARACHNOIDAE, which are organized after very different types, have 
always four pairs of feet. The Tardigrada form no exception in this 
respect; and although it may appear singular to find them placed in this 
class, yet this seems their most proper place; only they should be placed at 
the head, for they form the transition of the Arachnoidae to the Annelides, 
exactly as do the Cirripedia from the Crustacea to the Acephala.* 
The Arachnoidae are usually defined as Arthropoda wanting the anten- 
nae; this, however, is incorrect, for these organs are not wanting, strictly 
speaking, but take the place of the mandibles, which are absent, as will be 
shown hereafter. 
ORDER I. 
Cephalothorax multi-articulate. Special respiratory organs wanting. 
SUB-ORDER I. TARDIGRADA. 
Legs rudimentary. Abdomen wanting. 
Genera: Milnestum, Macrobiotus, Emydium. 
SUB-ORDER II. PYCNOGONIDAE. 
Legs very much developed. Abdomen rudimentary. 
Genera: Nymphon, Ammothea, Pallene, Phoxichilidium, Pariboea, Endeis, 
Phoxichilus, Pycnogonum. 
* [§ 295.] For a detail of the data which fully Stellung der Tardigraden, in Siebold and Kelliker’s 
justify this position of the Tardigrada, see Kauf- Zeilsch, III. 1851, p. 220. — Ep. 
mann, Ueber die Entwickelung und systematische 
