372 



COLLECTIONS FROM MELANESIA. 



explanation seems, however, to suggest itself as possibly applicable 

 to some cases of extremely generalized and indefinite types (e. g. 

 Reniera indistincta and Hi/meniacidon caruncula, which are common 

 to the British and Australian seas), viz. an independent origin of 

 the same species, or of what to a zoologist's eye is the same species, 

 at two different localities. The number of points by which it is 

 possible to distinguish species of (e. g.) Reniera, Hi/meniacidon, Amor- 

 phina, and Suberites from one another is so small, and these points 

 are so variable and so relative in their character, that it is quite 

 possible that the same end (i. e. the same specific characters) may 

 be attained by development in the same direction of two distinct 

 species, the result being a zoological but not a natural species, or, in 

 other words, of species which are distinct from each other but which 

 cannot be shown to be so. 



2. Distribution of ' Alert ' Species tvitJiin Australian Seas. 



List of the Species collected on the Australian coasts, or in the Ara- 

 furaSea, by H.M.S. 'Alert,' 1881, with their known distribution 

 in those waters. [The localities for Southern and Western 

 Australia, and in one or two cases for Port Jackson, are given 

 from previous writings ; the rest are those due to the ' Alert ' 

 investigations.] 



Note. — Where the distribution of a variety of a species is given, the distri- 

 bution of the typical form is also given (when Australian) opposite the name of 

 the species. The stars opposite the name of the variety refer exclusively to the 

 variety. 



