BIHANG TILL K. SV. VET.-AKAl). HANDL. BAND 20. AFD. IV. NIO 2. 13 



a Daphnia pnlex. Zenker '-') remarks however: >^Diese dem 

 Männchen von Dajjhnia ^ndix eigenthiimliehe Papille ist mit 

 Schuppen bedeckt iind gleieht in vieler Hinsicht der Spitze 

 am Schal enrande der Daphnia piiJea:, in die sie anch oft geleo;t 

 wird um den Körper des Thieres fester zwischen den Schalen 

 zn ziehen./ It wonld, however, be härd to conceive, why just 

 the male of the species in question sliould want suoh a papiUa. 

 P. E. Muller ^■') suspects the correctness of this idea of 

 Zenker. because the spine is never hollow>. Muller's state- 

 ment is certainly erroneons. The spine is hollow and when 

 in the state of exuviation tlie animarniust pal] the new spine 

 out from the old shell. AMiere, as in BythotrepJies, the caudal 

 spine is very long, the disengagement of the shellspine 

 during the exuviation is verv diiRcult, so that the spine can 

 only be partially palled out from the old shell, which remains 

 together with the appendices at the base, as P. E. Muller ''•) 

 has proved p. ii6. Moreover, for this species the prolongation 

 of the caudal spine is of importance as a balancing organ. 

 In Byfhoiriphes at the shedding process the cuticula breaks 

 square otf at the base of the spine. In Hyalocfaphnia also the 

 long spine would cause a good deal of trouble in the moul- 

 ting process, but here it is helped by the spine being splitted 

 along its under half, a phenomenon. I believe. 1 have observed 

 on an empty shell, Pl. II. tig. 40. 



In fact from this vve derive an explanation of the manner 

 in which the exuviation is performed, and the reason why in 

 the spe(>ies of the Dap/niia })i(Ipx-gron\) the spine grows 

 shorter with age and tinally bei-omes rediu-ed to a more or 

 less blunt ])rominence. 



By låter authors as Kurtz^'^) and Hellich^"*) the Daphnia 

 jndex-gvoui) has been still more split in to species, which, 

 however, ought all to be revised. I have already spöken about 

 a couple of these species, Daphnia «^w/?v>^« (Särs?) Hellich and 

 Daphnia (/ihbosa Hellich. ^^) Regarding Kurtz's *'^) Daphnia 

 obtnsa, which he first believed to be a synonym of Daphnia 

 2)nlc.r Lill.jeboro ^^'), but afterwards, when he had found the 

 male, proposed as a separate species, it ought to be observed 

 that the form, sketched by Kurtz, ^'^) Pl. I, fig. {), as the male, 

 is evidently a very young specimen of Daphnia pnlcx etc. 



Finally, concerning the form, the development of which 

 I have tried tx» trace here, I regard it as that one. which 



