32 



G. 0. SARS. 



[No. 8. 



rounded prominence. on which the anal opening is situated, and 

 exhibits above anotner process, whence the very long caudal 

 setæ originate. The distal part of the tail beyond the anal 

 opening is very narrow, and, on either side, armed with about 

 9 denticles, the exterior of which is non-ciliate and bifid, with the 

 outermost point the longer, whereas the remaining denticles are 

 simple and very delicate, as also densely ciliate along both edges. 

 The apical claws are comparatively small, and want every trace 

 of secondary teeth at the base, whereas at the anterior edge 3 

 slight serrations may be observed. 



As regards the internal organs, no essential differences can be 

 found from those in M. brachiata. The ova, when recently depo- 

 sited in the matrix, are exceedingly small and transparent, of 

 a faint rosy or violet hue, and globular in form. They rapidly, 

 however, increase during the embryonal development, dilating the 

 dorsal part of the carapace in the fore-described extraordinary 

 manner. On removing the numerous embryos, the so-called 

 alimentary layer („Nahrboden"), described more fully by Prof. 

 Weissman, and apparently affording a nourishing substance for 

 the embryos during development, is seen to project from the 

 dorsal face of the body wall. 



As stated above with regard to Daphnia Lumholtzii, also 

 of the present form the individuals belonging to the later gene- 

 rations, developing at the end of September, proved far less 

 productive than were those of the earlier generations, more than 

 2 or 4 embryos being rarely found in the matrix. Apparently by 

 reason hereof, the carapace of adult specimens exhibited at that 

 period a somewhat different aspect, its dorsal part being not 

 by far so expanded, and its form occurring more regularly 

 quadrangular. In some specimens, too, a distinct formation of 

 ephippium had tåken place (see Pl. 6, fig. 2). The struc- 

 ture of the latter was very similar to that in M. brachiata, 

 containing, as it did, but a single ovum. 1 It also exhibited, alike 

 as to size and structure, the most perfect agreement with a kind 



In M. paradoxa, Weissman, there are 2 transversely disposed egg-chambers, 

 as in the genus Daphnia, 



