510 PROF. F. J. BELL ON THE GENXJS ASTERIAS. [May 3, 



to examine the proportion between the greater radius and the width 

 of the base of the arm. The absolute measurements have already been 

 given ; these, when worked out, give the following proportions : — 



A. hispida— 2-1, 2-16, 2-18, 2-20, 2-4, 2-419, 2-.5, 2-6, 2-83, 2-85, 

 30, 3-4 ; 



A. rubens—3-0, 3-06, 3-25, 3-28, 3-50, 36. 



It is, then, so far clear that the base of the arms is wider in A. 

 hispida than in A. rubens for specimens of, or about, the same size. 



When we measure larger specimens of the commoner species, we find 

 the proportional value of the base of the arm to be 2'62, 2-86, 3-45, 

 and 3" 76. 



And this series falls in as well with A. hispida as with A. rubens ; 

 there is, however, this essential difference — that, in the former, R 

 varies between 1 9"5 and 7'5 millim., while in the case of ^. rubens 

 B has the minimum value of 42 millim., and a maximum value of 

 64 millim. 



After all, however, it is hardly necessary to raise the question of 

 proportions ; for A. hispida would seem to have never more than one 

 row of adambulacral spines, whereas A. rubens has frequently two ; 

 and, in the second place, there are absent from it the larger pincer- 

 formed " pedicellariae." 



Now arises an important and difficult question, — Is the absence 

 of these pedicellaria; any thing more than a specific characteristic ? 

 In other words, should it not be regarded as a mark of generic dif- 

 ference. Sufficient information is not yet at hand to justify any 

 final decision ; but I would suggest that the question be kept before 

 the minds of naturalists who busy themselves with these difficult 

 forms. I am myself inclined to believe that there is only a tendency to 

 their complete disappearance, and that the difference is purely specific. 



On the other hand, we know far too little as to the conditions of 

 existence under which these creatures live. Is it not possible that, 

 after all, A. hispida is but a pure variety, or a local race, or a form 

 stunted by living under disadvantageous conditions \ It is, indeed, 

 possible ; but, at present, the weight of evidence is in favour of 

 Forbes's original position, that A. hispida is a distinct species. 



(2) Characters of A. muelleri, Sars. 



The collection of the British Museum contains two specimens 

 bearing the "etiquette" of ^. muelleri. One, in spirit, was named by 

 Dr. Liitken, and it may therefore be regarded as a good, though, of 

 course, not by any means necessarily a " typical " specimen of the 

 species ; the other, which is dried, bears a label " Asterocanthion 

 (sic) midleri:" it was "purchased of Brandt;" but there is no 

 evidence as to who named it. 



The specimen named by Dr. Liitken has B, equal to 13 millim., 

 while /•=3, and the breadth of the arms at their base is 3*5 millim. 



^ Compare especially the interesting remarks of Prof. Eupert Jojies in his 

 \erj philosophical paper on Variation in the Foramiuifera (Monthly Micr. 

 Joiu-u. 1870 pp. 61-92) 



