470 Prof. F. J. Bell on Asterias rubens and the 



distinguished the " violet crossfish " from the " common 

 crossfish ; " some have asserted that they live together, others 

 that they are found apart ; some, more exact, have stated . 

 where they have found them living together and where they 

 have found them apart ; authors have varied in the extent to 

 which they believed them to be allied, from Miiller and 

 Troschel, who on p. 11 of their famous ' System der Aste- 

 riden,' regarded them as distinct, and on p. 126 in the 

 " Nachtrage " to the same work regarded them as " eins und 

 dasselbe," to the latest reformator systematis, who cannot 

 bring himself to put them in the same subgeneric division of 

 "Asterias." 



The differences of opinion which have existed will be easily 

 understood by one who will take either a named or an un- 

 named set of some dozen specimens from almost any locality, 

 so great are the variations of spinulation that may be detected. 

 Forbes distinguished the two, and gave figures to show the 

 differences in the form of their ambulacra (Brit. Starf. p. 99) ; 

 and the just weight of his authority has caused students of the 

 British fauna to keep the two forms apart. 



Without entering into full historical details on this point, 

 there are some more recent authorities whose views must be 

 noticed and discussed. 



In a very valuable paper published in this Journal in 1865 

 the Rev. Dr. Norman writes * : — " The species of Asterias, 

 both British and foreign, allied to A. rubens are extremely 

 difficult. We are unable to make up our minds whether we 

 have only one very variable form or many species. We have 

 described the two species distinguished by Forbes, A. violacea 

 and A. hisjrida, but for the present feel compelled to reserve 

 giving a positive opinion with respect to the value of their 



distinctive characters We have other closely allied 



forms in our seas, which scarcely fall under the description 

 of any species here described." 



Prof. Perrier in 1875 wrote f: — " Ainsi l'examen de tous 

 ces dchantillons te"moigne simplement du polymorphisme et 

 de la grande extension geographique de 1' Asterias rubens ; 

 mais les types divers que Ton peut observer et qu'on serait 

 d'abord tente" de separer sont unis par tant de formes inter- 

 mediaires, qu'il devient bientot impossible, quand on a beau- 

 coup d'individus sous la main, d'e*tablir aucune division 

 tranchde. Je ne saurais done jusqu'ici admettre V Asterias 

 violacea comme espece distincte." 



* Ann. & Mag. Nat. Hist. xv. 1865, p. 129. 

 t Arch. Zool. <ren. et exper. iv. p. 314. 



