176 THE VOYAGE OF H.M.S. CHALLENGER. 



be admitted that the perfect cirri of sexually mature individuals of the same species may 

 vary in size from eighteen to forty -five joints, and in length from 10 to 60 mm., the 

 characters of the cirri become altogether valueless for systematic purposes, and Bell's 

 formula? for expressing them briefly are of no use whatever, while the various schemes of 

 classification of the different specific groups which are given in this Eeport must be to 

 a large extent rearranged. 



Such an extensive range of variation in the characters of the cirri as is demanded 

 by Fischer's theory is one of which I have no experience whatever. Antedon eschrichti 

 ranges over nearly forty degrees of latitude ; but in the small Atlantic variety, as in the 

 large Arctic one, there are over forty joints in the cirri, which reach in the former to little 

 short of the length that they do in the latter type. The cirri of Antedon phalangium 

 have the same number of joints (about forty-five) in the Mediterranean as in the Minch, 

 though the joints are much shorter in the latter locality, so that the total length of the 

 cirri is reduced. Both these species thus resemble Antedon prolixa in having over forty 

 cirrus-joints in their southern, as well as in their northern variety ; and they thus afford no 

 support whatever to Fischer's theory of the great range of variation in Antedon tenella. 



If Antedon tenella of Scandinavia, the Arctic Ocean, and the Atlantic is merely a 

 dwarf or undeveloped variety of Antedon prolixa, young examples of the latter species 

 should present all the characters of Antedon tenella ; but this is very far from being the 

 case. Two immature individuals of Antedon prolixa in different stages of growth were 

 obtained by the " Varna " in the Kara Sea, and others at about the same stage as the 

 larger of these were kindly sent to me by Mr. F. Nansen from the dredgings of the 

 Norwegian North Atlantic Expedition near Spitzbergen. I do not think that any one 

 could possibly refer them to Antedon tenella. I have compared the smaller form with 

 an absolutely larger example of Antedon tenella which was dredged by the " Willem 

 Barents " in the Barents Sea at no great distance from the locality of the " Tegetthoff's " 

 dredgings. The calyx of the latter is altogether more robust than that of the former, and 

 the first radials are concealed, while both the axillaries and the second brachials have 

 assumed the shape characteristic of the adult condition. The former (Antedon prolixa), 

 however, shows its immaturity by the appearance of a considerable portion of the first 

 radials externally, by the shape of the axillaries and of the second brachials, which is not 

 that of these respective joints in the adult, and by the greatly elongated arm -joints. 

 The cirri, on the other hand, are much better developed than those of the more mature 

 and absolutely larger Antedon tenella, as seen from the comparison of measurements A 

 in the following table : — 



Antedon prolixa. Antedon tenella. 

 A. B. A. B. 



Length of cirri, .... 14 '5 mm. 33 - 5 mm. 11 mm. 18 mm. 



Number of joints, . 25 „ 34 „ 20 „ 26 „ 



