430 MR. W. p. SLADEN ON THE ASTEROIDEA 



From the fact that forms are separated by much smaller and 

 less strikiBg differences in an extensive genus than in one of more 

 limited scope, " species " in the larger group have often not such 

 clearly marked or conspicuous characters as those which are 

 presented by "varieties" in a less comprehensive genus. It 

 follows that the judgment should be very cautiously exercised 

 when tempted to embrace within a single species all the strongly 

 marked distributional extremes of any widely-spread type, how- 

 ever closely their connexion may seem to be preserved through 

 intermediate forms ; for in many cases these gradations are nothing 

 more or less than the links which indicate to us the development 

 of " species," and are, in short, the stages with which generally 

 we are unacquainted, owing either to the imperfection of know- 

 ledge, or more frequently by reason of their destruction through 

 the hostility of unfavourable conditions. 



Taking into consideration the advance which knowledge is con- 

 tinually making by means of the addition of new material from 

 hitherto unexplored fields, the process of too comprehensive 

 grouping would ultimately result in the formation of series 

 which, from their very unwieldiness, would require arbitrary 

 division for the mere purposes of classification and comprehension, 

 if the ordinary natural distinctions be ignored. Of course it will 

 be acknowledged that " species " are but arbitrary divisions after 

 all, and that a nomen triviale serves but to register the state of 

 information and our opinions upon certain forms of life ; but since 

 under such an aspect the organisms themselves stand as the out- 

 come of adaptation and the conditions of existence, the latter 

 factor being thus synonymous with Tiahitat or geographical posi- 

 tion, taken in its widest sense, it would evidently be a disadvan- 

 tage to science to lose the record of the influence which has been 

 exerted, and to sacrifice so simple an indication of the relative 

 position of a modified type within the area of its general occur- 

 rence. 



Stellasteb Belcheei, Gray. 



1847. Stellaster Belcheri, Gray, Proc. Zool. Soc. 1847, p- 1^ ; et Syn- 

 opsis of Starf. Brit. Mus. (1866), p. 7, t. vii. fig. 1. 



1866. Goniaster (Stellaster) Belcheri, von Martens, Ueb. Ostasiat. 

 Echin., Wiegm. Archiv, Jahrg. 32, p. 86. 



1871. Goniaster (Stellaster) Belcheri, Liltken, Vidensk. Meddelelser for 

 1871, p. 247, tab. V. fig. 3. 



