204 DISCOVERY REPORTS 



Sagitta innom. Fowler, 1908. 



5. lyra Johnston & Taylor, 1921; Bollmann, 1934 (part); Thomson, 1947 (part). 



S. maxima group Thiel, 1938 (part). 



I have discussed the vaUdity of this species in a previous report (David, 1955) and have shown that it 

 is separate from S. lyra with which it has been frequently considered synonymous. In the Southern 

 Ocean it exists in two main forms or races. One is predominantly subantarctic and the other is 

 predominantly antarctic. These two forms can be distinguished at all stages, except perhaps at the 

 very youngest ones. It is possible that they should be regarded as subspecifically, or even specifically 

 distinct. 



Horizontal distribution. Circumpolar, limited in the north by the subtropical convergence, and 

 in the south by the antarctic continental slope. Its maximum abundance is in the subantarctic. 



It should be noted here that very large specimens (up to 64 mm.) of S. lyra have been reported by 

 Tchindonova (1955) from the Kurile-Kamchatka trench, and from her Table i (p. 300) it looks as if 

 these specimens closely resemble S. gazellae, especially in the tail-segment percentages (10-15-4). 

 However, on p. 299 she records that many of these specimens had fully developed ovaries 'reaching 

 as far as the ventral ganglion, in some cases indeed nearly to the region of the head'; it is therefore 

 apparent that these specimens cannot be S. gazellae, for, at maturity stage IIP and beyond, all the 

 posterior teeth are lost in that species (David, 1955, pp. 243, 259), whereas the smallest number of 

 posterior teeth in the Kurile-Kamchatka specimens is 6 (at 47 mm.). It seems unlikely that these 

 specimens are S. lyra either, for the smallest number of hooks is 4-5 (at 64 mm.) and is more usually 

 6 or 7, whereas at maturity stages III and IV S. lyra has 3 or even less (Tokioka, 1939; Hamon, 1952; 

 David, 1955). It seems probable that these specimens are S. maxima, despite the very small tail 

 percentage given, for the head armature numbers fit that species well, as does the size range and the 

 fact that S. maxima is found in a similar environment in the North Atlantic. Examination of the paths 

 taken by the nerve cords from the ventral ganglion would have settled the question had the specimens 

 been figured, for in S. maxima the two posterior cords run down the inner margins of the fins on the 

 ventral side giving off branches to the fins at intervals, whereas in 5. lyra and S. gazellae these cords 

 run direct to the anterior insertion of the fins where they divide to run down the inner margins 

 of the fins on both the ventral and dorsal sides. 



{b) Sagitta marri 



Sagitta marri David, 1956. Sagitta planctonis and related forms. Bull. Brit. Mus. (Nat. Hist.), Zool. iv, 8, pp. 435-51. 



S. zetesios Fowler, 1907. 



S. planctonis (non Steinhaus) Ritter-Zahony, 191 1 (part); Jameson, 1914; Johnston & Taylor, 1921; Burfield, 1930 



(part); Bollmann, 1934 (part); Mackintosh, 1937; Thiel, 1938 (part). 

 S. planktonis (non Steinhaus) Hardy and Gunther, 1936. 



Ritter-Zahony recognized that this antarctic form differed from its close relations in warmer oceans, 

 but, for reasons which I have discussed elsewhere (David, 1956), regarded it as an intermediate form 

 between S. zetesios Fowler and S. planctonis Steinhaus. It is shown to be a separate species by the 

 shape and position of the seminal vesicles, and by other anatomical features. 



Horizontal distribution. Circumpolar; its maximum abundance is in the Antarctic. 



' Following Kramp(i93g) I distinguish five stagesof maturity numbered I-V for the common antarctic chaetognaths, stage I 

 being the immature forms and stage V the spent animals. At stage III the seminal vesicles are full and the ovaries somewhat 

 enlarged. At stage IV the ovaries are fully developed and breeding takes place. From most points of view the distinction 

 between stages III and IV is slight, and animals in both stages may be regarded as fully mature. 



