studies DM inariMO Osti-acods 9f) 



claws. Finally the C y t h e r e 1 1 i d s have, it is true, rather short and broad and powerful 

 furcal lamellae, armed with rather numerous claws, but the furca in these forms is of quite a 

 different type from that found in Cypridinids and H a 1 o c y p r i d s. 



^A^lich of these types is to be considered the most primitive? 



I consider it rather improbable that the very small furca in the C y t h e r i d s repre- 

 sents a primitive condition. Presumably a reduction has taken place in these forms (possibly 

 in connection with the powerful development of the posterior limbs). The different development 

 and type of the furcal lamellae and the great variation in the number and development of the 

 furcal claws in the other groups seem to indicate that, in spite of the fact that it presum- 

 ably had comparatively well developed lamellae, the furca of the Protostracods was, 

 all the same, very slightly differentiated; presumably it was armed with only a few claws. 

 The following facts also seem to support this assumption. Tliawnatocypris, which is, in many 

 respects presumably the most primitive genus among all H a 1 o c y p r i d s, has a furca that 

 consists of two relatively short, broad and powerful lamellae — like that of other H a 1 o- 

 cyprids. Each of these lamellae is armed with only two claws, situated distaUy; behind 

 these claws there is only a number of short spines. What perhaps strikes the observer of this 

 furca more than anything is its great resemblance to the furca in a closely-related group of 

 animals — the Cladocera. Without going so far as to say that this furcal type is the 

 most primitive, I wish, however, to point out one fact that may perhaps be considered 

 to point in this direction. In investigating the post-embryonal development of the Cypri- 

 dinids I observed that both in the sub-genera Doloria and Vargula and in PhUomedes the 

 youngest freely living larval stage is characterized by a furca consisting of two relatively short 

 and broad, but powerful, lamellae; each of these lamellae is armed distaUy with two rather 

 long and powerful claws, behind which there follow a number of short and weak spine-Uke 

 claws; cf. the special part of this work, fig. 21 of Philomedes glohosa and fig. 14 oiCypridina. 

 (Doloria) fectinata; only during the larval stages that immediately follow do these claws grow, 

 so that in these stages the transition between the distal and the proximal claws becomes uni- 

 form. G. W. MULLRR made the same observation (1894, p. 18.5) in the representatives of the • 

 Cypridinid group investigated by him, species of Vargula, Philomedes, Pseiidophiloniedes, Sar- 

 siella and Asterope; cf., for instance, G. W. MOLler's figure of a larval fvu-ca of the genus 

 Asterope, 1894, pi. 34, fig. 53. C. Claus, 1893, showed that the same condition is also charac- 

 teristic of the H a 1 o c y p r i d s (p. 286). ,,Das jiingste der beobachteten Stadien, leider nur 

 ein einzigesmal aufgefunden .... besitzt nur 2 Paare von Furcalklauen." During the first 

 freely living larval stage these forms thus have a furca whose type differs very much from that 

 of the mature individuals, but which shows, on the other hand, a comparatively close agree- 

 ment with the furca in Tliautnatocypris. — It is to be noted that the genus Tliaumaioqipris 

 was unknown to G. W. MtlLLBR in 1894. 



As will be seen from what has preceded, G. W. MOller does not say anything about Some ndduionni 

 the sexual organs of the Protostracods. This problem has rather great '"''"""■*■'•' "*""' ''"" 



-, ..... „ , '>r«nnizatinn of Uir 



difficulties. On accoimt of the conditions m the recent Ostracods and closely related Protostracods. 

 Crustacean groups, it seems to me most probable that both the testicles and the ovaries in Sexual organs. 



