708 



DE. W. B. CAEPENTEE ON THE STEUCTUEE, PHYSIOLOGY, AND 



out or nearly so, considerably beyond the margin of the disk. These appendages, for 

 which it seems to me that the designation given by Lamarck and adopted by Dujardin is 

 the most appropriate, were termed by J. S. Miller " auxiliary side arms," by Blainville 

 " rayons auxiliaircs," by Professor J. MiJLLER " ranken," and by Professor Edward Forbes 

 " filaments, jointed appendages, or simple arms." Any name which indicates a resem- 

 blance between these cirrhi and the Rays or Arms belonging to the calyx, is most inap- 

 propriate ; since the two sets of organs have no other point of resemblance than that 

 which consists in the articulated structure of their skeleton, whilst they differ in toto 

 as regards both their homological relations and their functional uses. The designations 

 respectively applied to them by J. S. Miller and by Blainville were so far correct, as 

 indicating their homology with those appendages of the stem in Pentacrinics which 

 these authors distinguislied by the same terms ; and it is expressly stated by the fonner 

 that " these arms, the formation of their joints, and their hook-like teimination, resemble 

 in every particular those of Pentacrinus Caput-Medusce, only that they are much shorter, 

 and formed of a less number of joints." That the " dorsal ciiThi " of Antedon have no 

 other function than that of mechanically fixing the animal, appears alike from the 

 extreme simplicity of their structure (which presents not the smallest trace of the com- 

 plex apparatus that is extended throughout the whole of the true brachial appendages), 

 and from observation of the animal in its living condition, as I have already shown in 

 the description of its habits (§§ 9, 10). 



26. The number of the Dorsal Cirrhi in Antedon rosaceus is by no means constant, nor 

 is their size uniform. It is by no means uncommon to find, even on the largest speci- 

 mens, one, two, three, and sometimes more of these organs in a very rudimental condi- 

 tion ; such being usually interposed between the larger ones at the extreme circum- 

 ference of the Centro-dorsal plate. In order to ascertain the range of variation in this 

 character (to which some systematists attach considerable importance in the discrimina- 

 tion of sj)ecies), I have carefully removed and laid upon separate tablets the entire clus- 

 ters of cirrhi possessed by twelve Arran specimens, which, although differing in size, 

 all presented every appearance of maturity ; and I find the respective numbers of these 

 organs to be as follows : — 



I. 21, of which 3 were rudimental. 



VII. 27, of which 3 were rudimental. 



Thus it appears that Professor Edward Forbes was not far wrong in stating the number 

 of these organs to be from twenty to thirty^. I cannot, however, by any means agree 



' History of Britisli Starfishes, p. 7. The number of cirrhi in Comatula Mediterranea is stated by Laxabck 

 at 30, by Professor JoH. MCxler at 30-40, and by Dtjjasdist at 20-26. — I have lately had the opportunity, 

 through the kindness of Mr. J. Gwtn Jeffreys, of examining a variety of Antedon rosaceus from the coast of 



