90 T.voK sKi)(isiii;i!c. 



Tilt' assumption that the littli and scxcuth linil)s arc cdi rclilcd to each ntlicr. Iliat 

 the lattor lias boon (IovoIojumI into a oKMiiinu ur^aii when, nwiiifj; to tlif (Icvelopment of tlic 

 former as an masticat'Orv organ, the breaking-up of the food had boon intensified, seems to be 

 open to criticism to a considerable extent. 0. Alm seems, as a matter of fact, to have realized 

 this, and his assumption is put forward very cautiously. 



Let us first examinf tiic family ([Uoted, the Cypridae. The fifth liiiil) in. for instance, 

 a Cypris — or Candona — species certainly seems to help pretty considerably in the breaking 

 up of the food, both directly by chewing and indirectly by holding the food fast and by pushing 

 it in under the two anterior masticatory appendages. There are thus reasons that support 

 the idea that in these forms, owing to the co-operation of the fifth limb in the process of chewing, 

 the breaking of the food is intensified and that, in connection with this, a rather considerable 

 increase of the defiling particles is produced. These forms thus seem to support G. Alm's state- 

 ment. On the other hand, however, there is in this family a number of forms which decided!}- 

 contradict this assumption. Thus the masticatory part of the fifth limb in the genera Ponto- 

 cypris and Pontocypria is sometimes not developed at all and often only slightly developed 

 and is furnished with a few weak, often soft and plumous bristles (as examples may be mentioned 

 PotUocyprh pellucida G. W. MCller and P. pirifera (i. W. Mt^LLER; the males of these species 

 have about two to four bristles on the reduced endopodite of this limb; cf. G. W. MtlLLER, 1894, 

 pi. 9. fig. 54 and pi. 10, figs. 23, 24). In these genera the fifth limb does not take any part 

 — or at any rate only a very slight one — in holding and breaking up the food; we have not, 

 even in the forms whose fifth limb is characterized by a somewhat greater number of bristles 

 than in the species mentioned above, any well-groimded cause to assume any essential increase 

 of the small defiling particles produced by mastication. In the males of the genus Erythrocypris, 

 e. g. those of the^. pallida G. W. MOller (cl G. W. MtJI.LBR, 1894, pi. 11, figs. 43, 44) the most 

 projecting part of this limb is quite without bristles; in the case of these forms any discussion 

 of the use of this appendage in the service of mastication may be considered superfluous. 

 Although in these genera it is thus impossible to think that we are justified in assuming that 

 any real increase in the number of the small defiling particles is produced by the activity of the 

 fifth limb, yet the seventh limb is in them apparently developed into an effective cleaning organ, 

 at any rate as effective as in the genera Cypris and Candona. Although a certain difference 

 may be observed in different forms with regard to the development of the seventh limb (the 

 degree of pectination of the end bristles), this has no connection at all with the development 

 of the bristles on the anterior side of the fifth limb. In the genera Argilloecia and Macrocypris, 

 and to a still greater extent in Paracypris the masticatory part (the endopodite) of the fifth limb 

 is furnished with numerous bristles and is also developed as a long branch pointing forward 

 (cf., for instance, G. W. MtJLLER, 1894, pi. 12, fig. 41, 42); in these genera this limb seems to help 

 considerably in intensifying mastication and thus possibly in increasing the number of the 

 small defiling particles as well. But the seventh limb is apparently not so well developed as 

 a cleaning organ in these forms as in the preceding genera; for instance it has no pectination 

 at all on the end bristles. In Paracypris ram (G. W. MOller), a form with a very powerful 

 ma.sticatory part on the fifth limb, we even find a seventh limb that is almost completely without 



