CLASSIFICATION 



371 



pair ot appendages divisible into podomeres ; in addition 

 to this, there is an almost universal absence of cilia in the 

 phylum, the sperms are usually non-motile, the muscles are 

 nearly always of the striped kind, and the body-cavity, which 



p., 0- — Eavly embryo of the Crayfish in the nauplius stage. 

 A in the upper part of the figure is the eye ; /. the labrum overhangmg the moutli 

 on each skJe Jf which are the rudiments of the antennules (aL), antennae (a-.), 

 ad mandibles {„,.) ; behind them is the rudnnent of the thorax and abdomen 

 (T-J) witl^ the -an"; (A). The rudiarents of the first three pa.rs of gangha 

 \g ga\ gm,) are seen through the transparent ectoderm. (From Lang, after 

 Reichenbach.) 



does not represent a true cttlome, is largely represented by 

 blood-spaces in free communication with the circulatory 



system. 



The phylum is divided into several classes, which are all 

 air-breathing except the Crustacea, the class to which the 

 Crayfish belongs and which also includes the Lobsters, 



Crabs Shrimps, Wood-lice, Barnacles, Water-fleas, &c. 

 ' B B 2 



