BOOK THIRTEENTH, 



AUACHNOIDAE. 



CLASSIFICATION. 



§ 295. 



The Arachnoiuae, wliich 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 

 speakinof, 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 : Milneslum, Macrohiotus, Emydium. 



SUB-ORDER II. PYCNOGONIDAE. 

 Legs very much developed. Abdomeu rudimentary. 



Clenera : Nymphon, Amynothca, Pallene, PhozichUidium, Pariboea, Endeis, 

 Phoxichilus, PycnogoJium . 



* [ 5 295.] For a detail of the data which fully Stt.'Uung der Tardigraden, in Sirbold and KtiUiker''B 

 Justify thi3 position of the Tardigrada, see Kauf- Zeitsch. III. 1851, p. 220. —Ed. 

 »nami, Ueber die Eutwickeluiig uud systematiäche 



