segment, and each composed of 9 joints clothed with scattered simple setse; 

 3rd joint much the largest, the 6 outermost joints comparatively short and 

 equal-sized. The 3 pairs of natatory legs normally developed and of essential 

 same structure, with both rami 3-articulate and nearly of equal size. The 

 last 2 pairs of legs very unlike the former, and reduced to simple small 

 3-articulate stems, with the middle joint very small, last rounded in shape and 

 provided with 2 unequal apical spines. Ovisacs very large, rounded oval in form. 



Body in the living animal highly transparent and nearly colourless, its 

 anterior part being filled up with a number of clear oil-bubbles of unequal 

 size and partly of a light orange colour. Eye replaced by a comparatively 

 large transverse patch of a light red pigment, in which, however, no trace 

 of refracting elements could be detected. 



Length of adult female 1.65 mm. 



Male unknown. 



Remarks. The above-described form is easily recognisable from any of 

 the other known Copepoda, both as regards its outward appearance and the 

 structure of the several appendages. I am much inclined to believe, that its life- 

 history will turn out to be a similar one to that stated by Malaquin for the 

 Mpnslrillidce, and that in the juvenile state this form leads a true parasitic 

 existence within the body of some invertebrate animals. 



Occurrence. Three specimens only of this remarkable form, all of the 

 female sex, have as yet come under my notice. One of them was taken, 

 many years ago, in the Christiania Fjord, at Dr0bak, the other 2 in the 

 Trondhjem Fjord, at Selven. All 3 specimens were captured, together with 

 other pelagic animals, by the aid of a plankton-net lowered to a depth of 

 about 60 fathoms. The living animal was seen moving through the water in 

 a similar jumping manner to that observed in most Cyclopoida. It was, 

 however, by no means particularly agile in its movements. 



