APPENDAGES. 439 



Thoracic appendages. In the lower members of the Malacos- 

 traca these form a uniform series, the members of which present 

 little or no departure from a common plan. 



In Nebalia they have the broad foliaceous character, with 

 faintly marked articulations, found in the Phyllopoda. The 

 short, narrow and jointed endopodite approaches the malacos- 

 tracan type, but the unsegmented exopodite and large flat 

 epipodite, notched on the outer side, are entirely phyllopodan 

 (Figs. 284 and 285). 



In Anaspides the eumalacostracan thoracic appendage is 

 found in what appears to be, in many respects, a primitive form 

 (Fig. 287 B). The 2-segmented protopodite is prolonged into the 

 stout ambulatory endopodite, and the flagellar exopodite springs 

 from the outer side of its second segment (basipodite). The 

 basal segment (coxopodite) bears on its outer side two simple 

 lamellar gills, the epipodites. 



The biramous character of the thoracic legs is preserved 

 throughout the Schizopoda, and in the larval stages of many 

 Decapods. In the majority of the latter it is only retained by 

 the three anterior legs of the adults (maxillipeds) though 

 in some of the Penaeidea and Caridea an exopodite persists 

 throughout life on all the legs. Three to five of the legs in the 

 middle of the thoracic series, in the Cumacea, retain the flagellar 

 exopodites, and they may be present in a reduced form on the 

 second and third thoracic limbs of the Chelifera. The Isopoda 

 and Amphipoda are devoid of thoracic exopodites. In the 

 Stomatopoda they are present on the last three legs. 



The epipodites present an interesting series of modifications 

 in the Malacostraca. Starting from the pair of simple append- 

 ages of Anaspides (Fig. 287) we find one of them, little modified 

 except that its attachment is shifted to the posterior or even 

 to the inner aspect of the limb, forming the thoracic gills of the 

 Amphipoda. The other appears, as suggested by Glaus, to 

 have undergone a change of function and to be represented 

 in the female by the oostegite in those orders of Malacostraca in 

 which the development of the young takes place in a brood 

 pouch. 



Oostegites are broad and almost membranous plates, attached 

 to the bases of certain of the limbs, which, overlapping those of 

 the other side, enclose a space beneath the ventral surface of 



