ZOOLOGY. 597 



The sexual parts do not lie posteriorly by the anus, 

 but at the root or base of the abdomen. 



It is moreover remarkable, that their mandibles are 

 perforated and pour a poisonous juice into the wounds 

 they inflict. They must be therefore regarded, like the 

 venom-teeth of Serpents, as elongated salivary ducts. 



The Crustacean families can also be named according 

 to the orders of their circle, namely, the Worms and 

 Crustacea, e. g. thus : 



ORDER I. Worm-Crabs Pfriemenkrebse. 

 Fam. 1. Entozooid Mussel-Insects 



2. Hirudinous Branchiopoda. 



3. Holothurioid Shield-Crabs. 

 ORDER II. Crustacean Grabs Scheerenkrebse. 



Fam. 4. Typical Crustacea Sea-Mantes. 



5. Asselkrebse Macrura. 



6. Arachnoid Brackyura, 



Ninth Class. 

 Tracheal, Alary Animals Flies. 



Typical Ancyliozoa. 



8517. Body tripartite, only three pairs of thoracic 

 legs, spiracula and wings. They divide, according to 

 the classes of their circle, into three cohorts, of Worm-, 

 Crab-like, and perfect Flies. 



As the wings are their characteristic organ, so also 

 must they be divided according to them, and not after 

 the cibarial instruments. Those wings which are de- 

 veloped to the least degree are the homogeneous, trans- 

 parent wings traversed by few tracheae or ducts Trache- 

 optera, as Flies, Bees, and Butterflies. 



Their chrysalis or pupa condition is perfect. 



Then follow wings having very numerous veins united 

 by transverse veins so as to form a network Dictyoptera y 

 as Neuropterous, Orthopterous, and Hernipterous Insects. 



The pupa is moveable. 



Finally, the anterior and posterior pair of wings become 

 wholly dissimilar to each other, the former being horny, 

 and the latter membranous in texture with reticulated 



