ARCHIV FOR MATHEMATIK OG NATÜRYIDENSKAB. B. XX. Nr. 11. 



Introduction. 



Many years ago (in the summer of 1885), when insti- 

 tuting some zoological inquiries at Risør, South coast of 

 Norway, I found in the tow-net some peculiar ova resem- 

 bling at first sight the usual pelagic fish-eggs abounding at 

 that time in the sea. On a closer examination, however, 

 they showed themselves to be very different in structure, 

 though of about the same size as those eggs. In the greater 

 number of the ova obtained, only the process of cleavage 

 was going on; but in a few cases the formation of the 

 embryo could be distinctly observed, and in one instance 1 

 witnessed the escape of the young one from the egg. This 

 was a normal Nauplius of a very simple structure, and at 

 once proved that the eggs were derived from some Crust- 

 acean animal. As to the nature of the latter, I was soon 

 informed, by finding at the same place two successive stages, 

 one of which was well known to me as an early larval 

 stage of Euphausiidæ 



As I was obliged to leave the place in a few days, 

 and the material at that time obtained was rather scanty, 

 I thought it advisable to defer the publication of these 

 observations, hoping soon to gain some better information 



