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



3'ear is defective. I (lid not tind in that year any young 

 females with spines, which were in a state of propagation. 

 But most of the specimens in the oolleetion of Augnst 1893 

 lepresent the fstage shown in the ligs. 22 — 23 whieh represent 

 females still with a short spine. Jn the fig. 23 one can already 

 see the ephippium thongh lightcohnired and senii-transparent. 

 On the other hand the specimens without spine were then 

 very scarce and at first I only fonnd a single specimen drawn 

 in the fig. 24. Bnt this one presents in some respeots a 

 jnvenile character, for instance in the outline of tlie back, 

 and its age may probably be estimated to be about three 

 weeks. The fig. 20 represents a young female with spine and 

 tooth on the neck. The figs. 19 and 25 are two young niales, 

 the age of which ean be stated exactly. They were hatched 

 from a female which was put in a glass on the 23''^ af August 

 and which only produced males. Of these two the fig. 19 

 was drawn on the 26*^, the specimen being thus not older 

 than at most 3^ 2 days and the fig. 25 on the 'M^^ of August, 

 thus at most 8 days old. If we compare this one with the 

 fig. 13 (smaller scale). representing an older stage, it is quite 

 plain that even in the niale specimens the spine becomes 

 reduced with the age, thongh not to the same extent as in 

 the females. 



Taking into consideration the investigations of Baird 

 which state, that the Ikq)hni(ls, thongh with longer intervals, 

 still continne to exuviate during the autumn and winter. or 

 in fact as long as circnmstances allow them to live, it would 

 have been of great interest to ccnitinue the observations still 

 longer, but I am sorry to say that this was not possible. 

 However, as it seems to me, several conclusions of a certain 

 interest may be drawn from these observations, although 

 there is really not much in them that was not known before. 

 only in my opinion, it was not rightly underst ood. 



If we peruse the literature about the Ikiphnia pulex- 

 group (ef. Bophnia Schoedler) which may be discussed at 

 first, we shall find, that De riEER ^) in his well-known work 

 as early as about 1770 knew and figured, Pl. 27, fig. 4, the 

 young of a Daphnia; moreover he pointed out the charac- 

 teristic marks of a young specimen, viz. a straighter dorsal 

 line and a straight spine stretching a little upwards from 

 the dorsal line. O. F. Muller -) did not take any notice at 



