BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND. 20. AFD. IV. N:0 2. 7 



and oon^equeiitly only youiig individuals, in wliich the trans- 

 parency is greatest, were examined and figured. At a låter 

 period of the investigations the chief aim seems to have been 

 to discover new species, which on the other hand led to an over- 

 rating of the vallie of differenees of form as specific charac- 

 teristics. Soine låter anthors, however. for instance P. E. Mul- 

 ler, ^^) have correctly accentuated the fact. that the outline of 

 the head and shell and the spine are subject to a considerable 

 variation, but at the same time Muller did not notice that 

 these variations are very often characteristies of ditferent 

 ages. Låter anthors have accepted the views expressed by 

 E. ScHQiiDLER and G. O. Särs; thns Bohuslav Hellich ^^j in 

 his work on the Cladocera of Bohemia (p. 21), published 

 1877 emphasizes: Bei der Bestimmung der Arten ist lianpt- 

 sächlicli der Bau des Kopfes, des SchnabeLs, der Sehale. die 

 Stellung des Schalenstachels mid die zwei ersten Abdominal- 

 fortsätze, endlieh die Bewehrung des Postabdomens zu beachten.» 

 In (X)mparing the series of developmental stages. exhibited 

 in my figures, the statemen t of Hellich nmst be quite nnte- 

 nable. As may be nnderstood from them, all the noted charac- 

 teristics change dnring the development of the individuals 

 fully as niuch as the siipposed si)eciHs diifer from each other, 

 diiferences upon which Hellich and other autliors have foun- 

 ded tlieir new species. Bnt at the same tinie Ave find. that 

 the transforniaticm is going on in a certain direction. The 

 outlines of the head and the rostrum change tbeir form. The 

 former is at årst in youiig specimeus niore rounded, but be- 

 comes vvith the increasing age concave beneath, soraetimes 

 verv deeply as shown in the figs. 9 — 12 or still more so in the 

 tig. 14. Aceording to my opinion, however. this is not a 

 variation depending upon greater age, but a monstrosity or 

 individna] variation; nevertheless, this has led Gr. O. Särs ^^ a) 

 to propose a new species. Daplinia aquilina fp. 216) [ef. 

 Hellich '"*) ]>. 84, fig. 8]. Their descriptions and the figure 

 of the form just mentioned agree with mine. except that the 

 spine remains in their specimens. thongh feebly developed or 

 situated above the median axis of the body which proves that 

 their specimens were younger than mine. With regard to the 

 dorsal outline I have already expressed my opinion. The fig. 11 

 represents a specimen with a humpy elevation on the back. 

 evidently the ephippium in an early developmental state. 



