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 which is the 

 homologue 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 which degeneration of 

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

 teristic feature. 



Of the characters to be em])loyed for the ]iurpose of com- 

 parison I will here further adduce only the compound eye 

 of the Cypridinidffi, 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. Tlius there takes place no fusion nor any overgrowth 

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

 in the EstheridjB. 



A renewed survey of the peculiarities of the Cypridinidte 

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

 coda to be brought into relation with the Esther ia-iy\it, thus 

 i^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 liand, 

 however, the Ostracoda exhibit much more primitive cha- 

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

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

 the appendages which are the homologues of the Euphyllopod 

 maxillffi. 



In answering the question as to Imw the peculiarities of the 

 Ostracoda admit of being reconciled with the origin of the 

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

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

 Estheridge 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 Estheridfe which 

 still possessed stalked eyes like Jiranchipus, and in which 

 neither the reduction of the mandibular palp nor that of the 

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

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

 existing Estheridfe in these respects were only developed 

 by them after the Ostracoda had branched off. 



• Cf. C. Claus, ' Die IJalocjpriden des atlantischen Oceana und Mittel- 

 meeres,' Wien, 1891, p. 28. 



