36 



DISCOVERY REPORTS 



it is: no pleopods — one pair non-setose — one pair setose, two pairs non-setose — three 

 pairs setose, two pairs non-setose — all five pairs setose. Thus in each instance where the 

 number of pleopods at any stage is known it is possible to predict the number of setose 

 pleopods after the next ensuing moult. 



EARLY FURCILIA STAGES 



Turning now to Enphausio superba in the samples used for the identification of Fur- 

 cilia stages, namely those from 70-cm. nets covering a number of seasons, and from the 

 oblique nets of the circumpolar cruise, fourteen different forms of Furcilia are recog- 

 nizable by the variation of development in the pleopods. 



These forms and their frequency of occurrence are shown in the table below, in which 

 is expressed the number of stations at which the various Furcilia forms were found. 



* In this form there are two types of larva recognizable : A, a smaller less developed form which normally 

 moults again into B, and B, larger and more developed and generally moulting into a form with five 

 terminal spines on the telson. 



Of the fourteen diff"erent Furcilia identified seven occur at one station only, and for 

 six of them the station is the same, namely WS 527. The remaining forms are found at 

 varying numbers of stations, but it will be noted that those occurring at the greatest 

 number of stations are as follows: (i) forms having four or five pairs of non-setose pleo- 

 pods, and (2) forms having four pairs of setose pleopods and one pair non-setose or all 

 five pairs setose. In other words these are dominant forms comparable to those in 

 Meganyctiphanes described by Macdonald. 



Analyses of the plankton samples taken with vertical 70-cm. nets at St. WS 527 show 

 that Euphausia superba larvae were present in a variety of forms, stated in Table XI 

 below. The number of different kinds of larvae and the frequency of occurrence are 

 shown and the average length of each stage is given. For completeness there have been 

 included Calyptopis stages and Furcilia stages with reduced numbers of spines ter- 



