studies on marine Ostracods 



101 



It is true that the f u r c a in Myodocopa is of a relatively uniform type, but, as is shown 

 on p. 95 above, it is by no means impossible that we are dealing here with a phenomenon of 

 convergence. In Podocopa this organ is subject to very considerable variations. 



The sexual organs vary very considerably in both Myodocopa and Podocopa 

 and it is certain that they cannot be adduced as evidence either for or against the classifica- 

 tion made by G. W. MiJLLER. These organs seem to be rather primitive in Myodocopa. 



Nor can the alimentary organs be used in support of G. W. MtlLLBR's view. The type 

 foimd in Myodocopa seems in all probability to be comparatively primitive. These organs are 

 not known in the Cytherella. 



A heart is found in C y p r i d i n i d s and H a 1 o c y p r i d s, but is absent in 

 P o 1 y c o p i d s and Podocopa. It existed in the P r o t o s t r a c o d s. 



Lateral eyes are only found in C y p r i d i n i d s. They were certainly to be 

 found in the Protostracods. A median eye is found in C y p r i d i n i d s and 

 most Podocopa. It existed in the Protostracods. 



The rod-shaped organ is found in Cypridinids and H a 1 o- 

 c y p r i d s, but is absent in the others. In the two former groups we are presumably con- 

 cerned with a phenomenon of convergence: see p. 96 above. 



Are there any other organs that might be used to support this classification of G. \^'. 

 Mullbr's? This question must, I think, be answered in the negative. 



It will be seen from this that G. W. MtJLLER's statement that the recent s t r a- 

 c o d s can be divided into two sharply differentiated natural main groups can scarcely 

 be considered as justified. The characters on which he based his assumption are partly 

 such as he himself considered primitive and partly such as we have reason to believe have 

 arisen by convergence. 



In my opinion the Cypridinids. H a 1 o c y p r i d s, P o 1 y c o p i d s 

 and Cytherellids form four well differentiated groups. The 

 Cyprids, Darwin ii lids. Nesideids and Cvtherids are, on the other 

 hand, comparatively closely related to each other; they might 

 conveniently be included in a h i g h e r c 1 a s s i f i c a t o r y unit, by 

 the side of the four groups mentioned above. Thus, in my opinion, the 

 Ostracods ought to be divided into five main groups*. 



This view coincides on the whole with that of G. 0. Sails ; it really differs from this 

 author's view only by the division of tlie Myodocopa into two groups, equivalent to the three 

 other groups, the Cypridinids and Halo c y p r i d s having been separated. It agrees 

 with C. Claus's view inasmuch as the H a 1 o c y p r i d s are not grouped with the C y p r i- 

 d i n i d s in a higher classificatory unit but differs from it because these two groups are taken 

 as sub-orders and because each of them is considered to be parallel to the group composed nf 

 the united families Cypridae, Darwinulidae, Nesideidae and Cytheridae. 



The question as to whether these five groups are to be considered as being of quite the 

 same classificatory value cannot be answered at present with certainty. 



♦ With regard to \.\k cliaiacleiixalion ui Ihesu groups 1 ufud uiily roffi- lu'n- U< llu- i{i-ou|i iliagaosi'.s given In-low. 



Furcii. 



SeJAtal organs 



lltinnilnri/ nrgoiis. 



Ilinrl. 



/ii/rii. 



KiiU-shapcd organ. 



OlhiT nrgnn'i. 



.S'mnmnry ofnii/rril- 

 icisin of G. H'. 

 Mailer's opinion thiii 

 the recent Ostracoih 

 are lo he divided into 

 Inn main ^roii/>s. 



The main groapa of 



the recent OslracoiU 



according to my 



