1 882.] On the Homologies of the Crustacean Limb. 791 



between the Phyllopodous and Ostracodous limbs, and the latter 

 are evidently derived from the Copepods, so that there is a con- 

 tinuous ascending series from the Copepoda through the Ostra- 

 coda to the Cladocera, and thence to the Phyllopoda. Hence, as 

 the young of the Copepoda are all Nauplii, and also those of 

 the Phyllopoda, it follows that the ancestral form of all the En- 

 tomostracous Crustacea, as originally insisted on by Fritz M tiller ■ 

 (Fur Darwin) was a nauplius-like animal. 



Comparison with the Dccapodous limbs. — Having studied the 

 homologies of the Phyllopodous limbs among themselves, and 

 also compared them with those of the Cladocera and Ostracoda, it 

 remains now to compare the thoracic appendages of the Phyllo- 

 pods with those of the adult Decapoda. At the outset, however, 

 it seems nearly impossible to compare the swimming legs of the 

 Phyllopods with the abdominal and thoracic appendages of Deca- 

 pods. The thoracic Decapodous legs are axially jointed, consist- 

 ing of an axis or protopodite, which is wanting in the Phyllopoda 

 and all lower Crustacea, with no endital lobes as in Phyllopods, 

 though the gill and flabellum of the Phyllopods are homologous 

 with the gills and flabellum of the Decapod. There is no such 

 relation or close resemblance as to lead us to infer that as regards 

 the nature of the thoracic and abdominal feet the Decapods have 

 descended from the Phyllopods. The Decapods have probably 



