;tj 



TAGE SKOGSBIOnO 



VibrtUon/ plates 



FuTca. 



ami N o s i il f i il s. a tact that 1 iil)sfrvi'(l inyst'lf and that is hy no means diffit'iilt to verify. 

 In this mode of crawling ton it seems expedient for several ])airs of legs to co-o|)erate. 



The C y p r i d i n i d s pass their lives — provided they are not exclusively swimming 

 or digging forms — partly in swimming about freely in layers of water just above the bottom, 

 partly in digging in the sand and mud of the bottom. ,,Zu einer eigentlich kriechendcn Be- 

 wegimg auf dem Grund sind die C y p r i d i n i d e n vermoge des Bancs ihrer Gliedmaalien 

 durchaus imfiihig; ich habe sie denn audi niemals in der Gefangenschaft sich in ahnlichcr 

 Weise bewegen sehen.'' (G. W. Mt)LLElt, 1894, p. 14.) In swimming and in digging the three 

 post'erior limbs have no function to fulfil; swimming is carried out exclusively by the second 

 antenna, digging, as in the Cytherellidae, by a couple of the anterior limbs (the mandible, 

 sometimes the second antenna as well) and the furca. 



The Halocyprids are exclusively pelagic forms; they swim only with the second antenna. 



The Polycopids cannot crawl. They either lie still on the bottom or take short 

 swimming trips to the layers of water just above the bottom. They swim with the first and second 

 ant<>nnae and the maxilla; as in the case of the Halocyprids, the other limbs are not 

 used in locomotion. 



We thus find that the fifth and seventh limbs do not take part or take only a very 

 slight part in locomotion in the case of freely swimming forms or in crawling forms in 

 which the crawling motions are helped by the more or less powerful upward and backward 

 natatory movements of the first antenna. In crawling forms whose first antenna does not 

 take part in locomotion the fifth and seventh limbs are developed as crawling legs. 



I do not mean by this, of course, that the method of locomotion was the only factor 

 that influenced the development of the two limbs just mentioned. Presumably, though not 

 certainly, other factors — both internal and external — have, as G. Alm also supposes, 

 cooperated; among such presumable factors may be mentioned the nature of the sub-stratum 

 on which these animals live and presumably the nature of their food as well. In any case the 

 method of locomotion must be considered to have been an important factor. 



After this excursus I return to my discussion of 6. W. MULLER's exposition of the organi- 

 zation of the Protostracods. 



1 have nothing to add about his assumption as to the vibratory plates; it is not 

 impossible that in this G. W. MUller has come very near to the truth, but it is by no 

 means proved. 



G. W. MtlLLER assumes that the furca of the Protostracods was of about 

 the same tvpe as this organ in Conchoecia. This seems presumably to be a some prematiu-e 

 assumption. 



Comparatively short and powerfid f ureal lamellae, armed with several strong claws, 

 i. e. about the same type as in Conchoecia. is found in Cypridinids, Polycopids 

 and most of the Halocyprids. In the other Ostracods we find fiu-cae of very varying 

 types. A number of forms, viz. C y t h e r i d s, have a very short and weak furca with a few 

 weak bristles. Others, viz. C y p r i d s and N e s i d e i d s, are characterized by relatively 

 long und narrow furcal lamellae, armed with a comparatively small number of bristles and 



