450 Prof. K. Grobben on the Genealogy and 



maxilla ; but, as opposed to the reduced maxilla of the 

 Euphyllopods, it is seen to be still traceable to the original 

 shape of the Phyllopod limb. The appendage wliich is the 

 honiologue of the second maxilla of the Euphyllopods is in 

 the Ostracoda " still indeed armed with a maxillary process, 

 yet chiefly constituted for locomotion as a foot " *, and there- 

 fore exhibits a general structural agreement with the following 

 appendages. The oral appendages of the Ostracoda conse- 

 quently undoubtedly display a more primitive shape than 

 those of the existing Euphyllopods, in wliich degeneration of 

 the mandibular palp and reduction of both maxillaj is a charac- 

 teristic feature. 



Of the characters to be employed for the purpose of com- 

 parison I will here further adduce only the compound eye 

 of the Cypridinidai, which has persisted exclusively in this 

 Ostracod family. The compound eyes of Cypridina retain 

 their original position at the sides of the head and have short 

 stalks. Thus there takes place no fusion nor any overgrowth 

 of the two eyes by a reduplicature of the skin, as is the case 

 in the Estheridee. 



A renewed survey of the peculiarities of the CypridinidjB 

 reveals, on the one hand, characters which allow the Ostra- 

 coda to be brouglit into relation with the Esther ia-iy^Q, thus 

 — the bivalve character and the extent of the shell, which 

 encloses the entire body, the ventrally flexed form of the 

 furca, and the swimming-foot-antenna. On the other hand, 

 however, the Ostracoda exhibit much more primitive cha- 

 racters in the short-stalked compound eyes of the Cypridi- 

 nidee, as well as in the development of the mandibles and of 

 the appendages which are the homologues of the Euphyllopod 

 maxillge. 



In answering the question as to how the peculiarities of the 

 Ostracoda admit of being reconciled with the origin of the 

 latter from Estheridse, it is seen to be impossible to suppose 

 that the Ostracoda are to be derived, like the Cladocera, from 

 Estheridaj with the characters which they at present possess. 

 On the contrary, it may be assumed with good reason that 

 the Ostracoda sprang from old forms of Estheridse which 

 still possessed stalked eyes like Branchipus, and in which 

 neither the reduction of the mandibular palp nor that of the 

 two pairs of maxillai had appeared, but in which the latter 

 had the original foot-like shape. The peculiarities of the 

 existing Estherida? in these respects were only developed 

 by them after the Ostracoda had branched off. 



* Cf. C. Claus, * Die Halocypriden des atlantisclien Oceans und Mittel- 

 meeres,' Wien, 1891, p. 28. 



