2 G. O. Sars. 



mud and dried aquatic plants from the same tract. He 

 observed, however, that the fresh-water fauna of that region 

 had, according to his investigations, turned out to be ex- 

 tremely poor, and indeed the alcoholic samples received 

 did not contain anything but some larvæ of Copepoda and 

 a few small Lynceids. There therefore at first appeared to be 

 very little chance of good results for the hatching operations. 

 These were immediately commenced, however, in the usual 

 manner, small parcels of the material being introduced into 

 carefully-prepared aquaria, which from time to time were 

 examined by the aid of a hand-magnifier. The final results 

 of these hatching operations, which have been continued for 

 several years, have however, as shown by the present paper, 

 turned out to be very successful, and have yelded quite an 

 unexpectedly rich harvest. As early as the first summer 

 some interesting forms appeared in my aquaria, one of 

 which, Iheringula paulensis G. O. Sars, has been treated 

 of in detail in a previous paper, and during the succeeding 

 years many additional forms have been raised, partly from the 

 same material, partly from some additional mud kindly sent 

 to me subsequently. Indeed, I have now convinced myself, 

 that by far the best method of studying extraneous fresh- 

 water Entomostraca is that here practised, viz, to raise the 

 species from dried material taken in the respective regions 

 from suitable localities. True, the arrangement of the 

 aquaria for this purpose requires much care, and also much 

 expenditure of time to examine the aquaria, and to await 

 the development of the Speeres; but, on the other hand, it 

 is evident that the investigations made in such cases admit 

 of a very superior completeness both morphologically and 

 biologically, than those instituted on preserved specimens. 

 Indeed, it is both very amusing and instructive to watch 



