b. ALLEGED DIFFERENCES BETWEEN EUROPEAN AND INDO-PACIFIC SPECIMENS OF THE SAME SPECIES. 



Attention has been called to some supposed relations between European and Indo- 

 Pacific specimens, the chief of which is that the latter possess a greater number of teeth than 

 is found in specimens of the same species from European waters: — a relation, which, if 

 proved to be true, would be of considerable interest. The instances on which it has been based 

 are as follows. 



AiDA (op. cit.) called attention to this supposed fact in his record of 'bipimctata ; but 

 there is no doubt in my mind that he had before him, not bipunctata Ouoy and Gaimard, 

 but Bcdoti Béraneck (compare pp. 7, 8 above); this instance therefore I believe to lapse. Aida 

 also made the same comparison with hispida Conant; but here again it is practically certain 

 that he was not dealing with Conant's species (compare p. 20). Donc.\ster expresses his 

 agreement with Aida on this point about 'hispida, but mentions no such differentiating details 

 of the specimens, as would make it clear to a reader that he had Conant's species before him. 



DoNCASTER further states that in enjlata from the Maldive Archipelago, as compared 

 with European species, the tail segment is 'rather shorter in proportion to- the trunk, and the 

 teeth are sometimes more numerous. Exactly the same differences are described by Aida between 

 the S. enjiata found in Japan and those of European waters'. Aida however had recorded for 

 Japan (9 — 10 ; 6 — 8 : 10 — 11) much the same formula as Grassi for the Mediterranean 

 (9 : 6 — 9 : 9 — 11); and he reported the tail segment as '/5 to '/e of the total length, while 

 Grassi described it as little less than a quarter; there is practically no difiference here. Doncaster 

 did not publish the number of teeth on which his statement was based. A reference to the 

 table on jjage 9 above will show that the teeth in old specimens of enjlata are often more 

 numerous than Grassi recorded, but his largest specimen was only 20 mm. long, and did not 

 differ greatly from the Siboga figures for that length. 



For serratodentata Doncaster records 18 — 20 posterior teeth and 10 anterior, "instead 

 of 12 and 8 respectively in European waters". The following table bears upon this point. 



On the whole the teeth recorded are more numerous in Pacific than in European 

 specimens, but Krohn's record of 1 8 posterior teeth from Messina upsets at once any conclusion 

 that might be drawn as to this being a mere matter of geographical position. 



There certainly is a great difference between the table of serratodentata in Biscayan 

 Plankton (p. 59) and that given in this Report (pp. 20, 21); they were based respectively on 

 thirty eight and thirty specimens; roughly speaking, the number of posterior teeth in a Pacific 

 specimen is doublé that of a Biscayan specimen at the same length. It is possible that this 

 may be correlated with the respective temperatures at which the specimens live, but a long 



