68 DISCOVERY REPORTS 



also given. The numbers of two- and one-spined larvae are too small to be really in- 

 dicative of what happens, but from the remaining groups it is clear that the change in 

 form of the rostrum can take place in any one of a number of larval stages, the spinous 

 form tending to be more common in the later than in the earlier stages. 



Table XXVIII. Presence or absence of the rostral spitie in late Fiircilia larvae 



The examination of these larvae shows that development in Euphausia superba in the 

 later Furcilia stages is not a rigidly fixed process in the degree of development of par- 

 ticular appendages in relation to one another. It is only possible to indicate in the most 

 general way the track that development takes. 



The analysis also shows what has been referred to at the beginning of this section, 

 namely that in this species the change in form of the antenna is preceded by changes 

 equally fundamental in character in the mandible and the first thoracic appendage. This 

 furnishes a strong argument against the use of the term Cyrtopia for larvae with altered 

 form of the antenna. It may be added that John in his paper on the southern species of 

 Euphausia, about to be published, shows that in different species the change in form of 

 the antennae can precede, or accompany the changes in the mandibular palp and ist 

 thoracic limb. 



DESCRIPTION OF FURCILIA STAGES 



For the purpose of this description the Furcilia forms are classified in the following 

 stages : 



First Furcilia (p. 69). Pleopods non-setose. In this stage are included all larvae, in 

 advance of the 3rd Calyptopis, having simple non-setose pleopods. 



Second Furcilia (p. 76). Pleopods setose, postero-lateral and terminal telson spines 

 unaltered. This stage includes larvae with setose pleopods, up to five pairs in number, 

 having seven terminal spines on the telson and the postero-lateral spines unaltered. 



Third Furcilia (p. 84). All pleopods setose, seven terminal spined telson, postero- 

 lateral spines altered. 



Fourth Furcilia (p. 88). Five terminal spines on the telson. 



Fifth Furcilia (p. 92). Three terminal spines on the telson. 



