10 R. LUNDBERG, DEVELOPMENT OF THE DAPHNIDS. 



it is evident that an older form is tlie original of that iigure. 

 As abovp men tion ed niost of tlie antliors liefore Leydig agreed 

 in regarding Daphnid longispina O. F. Muller as a young 

 form or, as Baird "') and others do, as a variety of Ddphnia 

 2mlex. Bnt now Leydig *-) declared on account of tlie ditfe- 

 rences he had obsei-ved in tlie males of the respective species, 

 that Dap/niia maffiia. pitlcr and louifispina were genuine spe- 

 cies, wliicli afterwards became the general opinion. Wheii 

 examining Leydig's ^-') figure of the niale of his Daphnia 

 lonfii.spina (Pl. II, lig. 19) there can be no doubt, that this is a 

 young speeimen still in possession of the triangulär promi- 

 nence which cliaracterizes the young forms, although it is 

 situated farther back than (m my figures. The figure of a 

 female, given l)y him. is evidently also a young, just as is De 

 Geer's ^) figure. ([uoted by him as a synonym. P. E. Muller ^■') 

 has tried to solve the (juestion about the Daphnia Ifnigispiiia 

 of his {'elel)rated fellow countrynian's. He considers O. F. 

 Muller's and Leydig's species as forms of longispina, though 

 the first mentioned author means a form witli a long spine and 

 the second a form with a short one. By this arrangement, 

 however, the ([nestion is by no means elucidated or solved. 

 In direct op])ositioii to his namesake he regards the form of 

 De Geer, ') fig. 1 — 4. Pl. 27. as JJaphnia pulcx. This species. 

 which also sometimes has varieties with a spine, difFers from 

 the othei- in the armature of the abdomen. Uapliina index 

 has all its aculei caudales of the same length, but in Daplinia 

 longispina these »aculei v decrease in size towards tlie back. 

 This characteristic can not, howevei", be considered as very 

 important. In 1113- opinion the name. Dap)hnia longispinu, 

 ought to be stricken ont from the nomenclature, where it has 

 caused so much confusion. 



When O. F. Muller -) proposed his new species DapJmia 

 pennata, he did so chiefly because the Monoculus pulex of older 

 authors comprehended the whole of the genus Daphnia esta- 

 blished by Muller in the same work. Since the presence or 

 absence of a spine had been for former investigators, e. g. De 

 Geer ^) and more recent ones. an all important characteristic 

 for those species of the genus Monoculus, which correspond 

 with Muller's genus Daphnia, he thought it best to establish 

 a different species — Daphnia pennata — for those (older) 

 forms, in which he did not find any spine or oiily a feebly 



