PTEROBRANCHIA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 561 



The evidence as to the number of arms may be given in a tabular form, as 

 follows : — 







Number of Individuals. 





Sex. 



Number 





Remarks. 







of Arms. 



Stat. 5. 



Stat. 94. Total. 





Female 



10 



13 



1 

 2 15 





>j 



11 



3 



3 



In one of these cases the evidence 













for the occurrence of more than 













ten arms was not conclusive. 



)) 



9 



1 





1 





Unknown 



10 



5 



9 



14 





>) 



11 





1 



1 



Perhaps not more than ten arms. 



)! 



12 



... 



1 



1 



)i )) 



Male 



12 





2 



2 





J) 



11 



... 



1 



1 







38 





It is thus clear that the majority (29 out of 38) of the zooids examined have ten 

 arms; that of this number 15 were proved to be female, while the remaining 14 may 

 have belonged to that sex ; and that no individual proved to be male has ten arms. 

 It should be noted, however, that we are assuming, with Andersson, that the specimens 

 from Stations 5 and 94 belong to the same species. Of three zooids in which twelve 

 arms are certainly or doubtfully present, two were ascertained to be male. There is 

 evidence that the female may occasionally have eleven or nine arms instead of the 

 normal number (ten), and that the male may have only eleven arms instead of the 

 number (twelve) stated by Andersson to be characteristic of that sex. The evidence of 

 the occurrence of eleven arms in two female specimens appears to be quite satisfactory. 

 In counting the arms, an arm-bud has been reckoned as an arm even though, as in one 

 of these two, it is very small and but little developed. 



Evidence of a similar nature was obtained from sections of the material received 

 from Stockholm. In six series of sections of female zooids, five arms could be counted 

 on one or both sides ; while in a single series of sections through a male zooid twelve 

 arms were ascertained to be present. 



Turning to the Discovery specimens described by Ridewood as C. hodgsoni, the 

 number of the arms has been re-examined in eight series of sections, with the following 

 result : — 



Ten arms are present in 2 female zooids, and in 2 others in which the gonads are 

 too minute to be certainly distinguishable as ovaries. Ten is probably the number of 

 the arms in 1 other case in which the sex is not determinable. Three zooids are male ; 

 and of these 1 has twelve arms, 1 has not less than eleven arms, and 1 has not less than 

 ten arms, while the possibility of the occurrence of twelve arms is not excluded. 



