PODOBRANCHI^ AND EPIP0DITE5. 167 



the podobrancliia is taken by a broad soft membranous 

 plate entirely devoid of branchial filaments {e^f). Thus, 

 in the series of the thoracic limbs, on passing forwards 

 from the third maxillipede, we find that though the plan 

 of the appendages remains the same ; (1) the protopodite 

 increases in relative size ; (2) the endopodite diminishes ; 

 (3) the exopodite increases ; (4) the podobranchia finally 

 takes the form of a broad membranous plate and loses its 

 branchial filaments. 



Writers on descriptive Zoology usually refer to the 

 parts of the maxillipedes under different names from those 

 which are employed here. The protopodite and the endo- 

 podite taken together are commonly called the stem of 

 the maxillipede, wliile the exopodite is the jpalp, and the 

 metamorphosed podobranchia, the real nature of which 

 is not recognised, is termed the flagellurn. 



When the comparison of the maxillipedes with the 

 abdominal members, however, had shown the funda- 

 mental uniformity of composition of the two, it became 

 desirable to invent a nomenclature of the homologous 

 parts which should be capable of a general application. 

 The names of protopodite, endopodite, exopodite, which 

 I have adopted as the equivalents of the " stem " and the 

 "palp," were proposed by Milne-Edwards, who at the 

 same time suggested epipodite for the *'flagellum." And 

 the lamellar process of the first maxillijDede is now very 

 generally' termed an epipodite ; while the podobranchlse, 

 which have exactly the same relations to the following 



