100 



INVERTEBRATE ZOOLOGY. 



Somites. 



I 1 



Appendages. 

 Anti Rudimentarj'. 



W 





II 



III 



IV 



V 



VI 



VII 



VIII 



IX 



X 



XI 



XII 



L XIII 



r 14 



15 

 16 



17 

 18 

 19 

 20 



r o 



I? 



Anta 



Md 



Mxi 



Mxo 



Mxp 



Li 



Lo 

 La 



L4 



L5 



L« 

 L. 



Pli 

 PI2 

 PI3 

 PI4 

 PI5 

 PL 



Large. 



Lamellate, folded over the others. 



With brood lamellae in female. 



Endopodite serves as gill. 



Expodite large, containing air chambers. 

 Serves also as protection for the true gill. 



Without gill, forming part of tail. 

 Central tail piece, fused with 19. 



7 I , Study of a cross-section. The internal anatomy of PorceUio is very 

 similar to that of Type XI, and need not receive especial attention. A general 

 idea of the relationship of the different parts may be obtained from a cross- 

 section prepared as in (59. The section should be taken through the thorax 

 and w\\\ serve as a type to illustrate the relationship of systems in Arthropods 

 in general. In the center will be the alimentary canal : above this will be the 



