APPENDAGES. 345 



tactile and olfactory sense organs, and in many Malacostraca 

 carry an otocyst (cf. p. 350) in the basal segments. 



The second antennae are generally biramous. Beside their 

 tactile function they are often powerful swimming appendages. 

 In the anostracous Phyllopods numerous secondary lobes 

 are developed in the male and they are prehensile. In the 

 Malacostraca the 

 exopodite has often 

 the form of a simple 

 scale, which however 

 is (in the develop- 

 ment of Euphausia] 

 derived from an 

 articulate flagellum. 

 In the nauplius larva 

 a masticatory lobe is 



present *nd the ap- FIG. 239. Gammarus pulex (after G. O. Sars). A', A" 



the two antennae ; F', F? the first and seventh ambulatory 



Dendage is paroral, leps (thoracic legs 2-8) ; Kf maxllliped ; Sf first abdominal 



J'^ legs " 



a condition appar- 



ently permanent in the Trilobites, in which group they formed 

 the first pair of jaws. The antennal excretory gland opens 

 when present on the coxopodite, or when there are three seg- 

 ments of the protopodite, on the second of them. 



The mandible is characterized by the development of the 

 coxopodal endite into a cutting and masticatory blade, the 

 remainder of the appendage constituting the mandibular palp. 

 TJiis usually consists of the basipodite" and a few- jointed endo- 

 podite, but in some Copepods (Fig. 260) and Ostracods (Fig. 

 253) an exopodite is found in addition. The palp is in 

 some cases absent altogether. 



The two pairs of maxillae (Fig. 240 c and d) are generally 

 short and jaw-like, consisting mainly of the protopodite and 

 a short endopodite, the segments of which are produced into 

 cutting blades (endites) ; a simple lobed exopodite is however 

 frequently present. Hansen concludes that the two inner 

 blades of the first maxilla belong to the 1st and 3rd segments 

 of the protopodite. The maxillary excretory gland (the " shell 

 gland " of many Entomostraca) opens on the 2nd maxilla. 



Often associated with the formation of a cephalothorax, modi- 

 fication of one or more of the anterior thoracic limbs has 



