AZOEEAN GROUP. 7 



to me to doubt for a single instant the truthfulness of the asser- 

 tion ; but what the exact meaning may be (as Mr. H. C. Watson 

 has pertinently asked) of such expressions as ' all the islands,' 

 ' toutes les iles,' ' tout Farchipel,' &c., more particularly when 

 used by naturalists who confessedly have explored but imperfectly 

 some of the remote detachments of the group, and one of which 

 was not visited by them even at all, is an enigma which I must 

 confess myself totally unable to solve. In my own instance, if out 

 of an archipelago of ten islands a given species had been ob- 

 served on nine of them, and even if I felt well-nigh certain that 

 it would be met with equally on the tenth, still nothing would 

 induce me to call that species actually 'universal' until the one 

 missing link had been proved to a demonstration. I should un- 

 doubtedly express my belief that it would eventually be ascer- 

 tained to be universal ; but, holding the most perfect accuracy 

 to be a sine qua non, and knowing by experience how often an 

 organism is non-existent upon an island, or rock, while it abso- 

 lutely swarms on another which belongs to the same assemblage, 

 I could not risk my reputation by making a positive statement 

 which it is at least possible might turn out ultimately to have 

 been fallacious. Therefore I will not hold myself answerable for 

 the complete truthfulness of the particular idioms, published by 

 others, to which I have just called attention ; but in those 

 cases where I have reason to feel dissatisfied with the value of 

 the evidence for these professedly wide habitats, I shall, while 

 indicating (in the local catalogue) the asserted universality by 

 quoting the species under ' all the islands ' (as indeed can 

 scarcely be avoided), cite, at the same time, the exact authority, 

 alongside, which must be responsible for the entry. 



Although unwilling to make the above remarks, I look 

 upon them nevertheless as neither more nor less than a neces- 

 sity ; for, out of the 176 species which have been ascertained to 

 occur in the Madeiran group, only four (namely ihelt.erubescens, 

 paupercula, and polymorpha, and the Clausilia deltostoma) 

 have been found as yet to be absolutely universal, and that 

 too in an archipelago composed of but Jive islands, and in spite 

 of the most careful researches of many naturalists extending over 

 a period of nearly fifty years ; yet, out of the 69 species which 

 were met with by Morelet and Drouet during a single sojourn of 

 five months at the Azores (the H. niphas, Pfr., and Bulimus 

 solitarius, Poir., not having been found by them at all, and the 

 H. advena, W. et B., being erroneously admitted into the 

 Azorean list), no less than 23, or exactly one-third, are said to 

 inhabit ' tout 1'archipel,' i. e. the whok nine islands which 

 constitute that far more widely scattered cluster. Judging 

 from the analogy of the Madeiras (and the case at the Canaries 



