CLASSIFICATION OF AETHEOPODA. 229 



merism, as compared, that is, with that which it exercised in the 

 Annulata. 



I give the following review of the Classification of the Ar- 

 thropoda : 



A. Branchiata. 



I. Crustacea*). 



a) Entomostraca. 



1. Cirripedia. 



Balanus, Coromila, Lepas. 

 Rhizocephala. 



Sacculina, Peltogaster. 



2. Copepoila. 



Cyclops, Cyclopsina, Corycseus, Sapplurina. 



Siplionostomat). 



Caligus, Ergasilus, Dichelestium, C'hondracantlm-, 

 Achtheres, Lerna?a, Lernaeocera, Pcnella. 



3. Ostracotlat). 



Cypris, Cypridina. 



4. Branchiopoda§). 



Cladocera. 



Daphnia, Sida, Polyphemus, Evadne. 

 Phyllopoda. 



Branchipus, Apns, Limnadia. 



b) Malacostraca||). 



1. Thoracostraca (Podoplithalma). 

 Schizopoda. 



Mysis, Euphausia, Thysanopus. 

 Carida*"). 



Crangon, Alplieus, Palsemon, Hippolyte, Peneus. 

 Decapoda. 



Macrura. 



Astacus, Palimirus, Galathea, Pagurus. 

 Bracliyura. 



Carcinus, Maja, Hyas, Dromia, Dorippe. 

 Cumacea**). 

 Cuma. 



* The appendages are complete in each segment of the body, although they often 

 undergo adaptive modifications. They either function directly as respiratory organs, 

 or the latter are very closely connected with them. 



f A lai - ge number of families are brought together into this special subdivision, 

 owing to the more or less complete parasitism they exhibit ; they may be distin- 

 guished from free-living Cojaepoda, but must be considered as derived from them. 

 The Ehizocephala bear the same relation to the Cirripedia. 



X They show signs of affinity with the developmental stages of the Cirripedia, by 

 the possession of a mantle-fold, which foi'ms the two-valved shell. 



§ This division seems to be the most direct continuation of the Nauplius-form, 

 from which stage it is derived by the mere formation of metameres, while the appen- 

 dages themselves undergo only slight modifications. 



|| These forms, which are allied to the preceding division by the Nauplius stage, 

 which is seen in Peneus and Euphausia, represent on the whole a further development 

 of the Crustacean organisation. 



^[ Connect the Schizopoda and Decapoda : sometimes they are classified with the 

 latter. 



** They correspond to the lower developmental stages of the Decapoda, for they 

 closely resemble the Schizopoda in their form of body. The eyes have no movable 

 stalk, and so far they approximate to the Arthrostraca. 



