258 THE VOYAGE OF H.M.S. CHALLENGER. 



sponges were commonly obtained. We shall, however, return to tke question of 

 bathymetrical distribution later on, and refer to it in this place only in explanation of a 

 very striking fact which meets us at the outset. 



Comparatively little is as yet known of the geographical distribution of sponges at 

 large, and still less, of course, of the distribution of the Monaxonida. 



Vosmaer,^ it is true, has dealt with the subject in some detail, and constructed tables 

 both of geographical and bathymetrical range, but his results are far from being 

 satisfactory. His list shows that sponges are most abundant in the Mediterranean and 

 Atlantic Oceans, but, as he himself points out, this is only because the Mediterranean and 

 Atlantic have been more or less thoroughly explored — witness Schmidt's works on the 

 Atlantic, Adriatic and Algerian sponges, and Carter's researches on the Atlantic 

 sponges obtained by the " Porcupine," — while the sponge faun^ of other seas and oceans is 

 or has hitherto been almost entirely unknown. Hence it follows that the results of the 

 Challenger Expedition taken alone are likely to give more trustworthy information on 

 this head than those of all previous workers, simply because the observations were ex- 

 tended more impartially over an enormous area. 



Vosmaer, then, makes six geographical areas, which, he tells us, are "voUkommen 

 kiinstlich ; " viz., Mediterranean, Atlantic Ocean, Pacific Ocean, Indian Ocean, Arctic Ocean, 

 and Antarctic Ocean. Such an arrangement may be very suitable for general purposes, 

 but is obviously inapplicable to the present case, as will be seen by a glance at the chart 

 which illustrates our remarks on this head. The areas which we distinguish (vide Chart) 

 are necessarily made to suit our own requirements. This is unfortunate, as it makes 

 comparison a somewhat more difficult matter, but it cannot be avoided. 



One or two peculiarities strike us in examining Vosmaer's table. Leaving out of 

 account the Spongillids, with which we are not concerned in this place, we find here set 

 forth the geographical distribution of 74 genera, or so-called genera, of Monaxonid sponges. 

 Of these, two, viz., Amjihilectus and Clathria, are stated to be cosmopolitan. The first, 

 inasmuch as it is, as is stated^ by Vosmaer himself, "nur ein vorliiufiges Aushilfe- 

 Genus, wo alle diejenigen Desmacidinen untergebraclit sind, von welch en keine besondere 

 Merkmale bekannt sind, wodurch sie zu einer anderen Gattung kommen sollten," might 

 naturally be expected to be more or less cosmopolitan, while we are inclined altogether 

 to deny the cosmopolitan character of the second {Clathria), at any rate until more 

 evidence is forthcoming. It is not a little surprising to find that, according to Vosmaer, 

 Monaxonid sponges^ have been hitherto altogether imknown from the Antarctic Ocean, 

 and that only nine genera are recorded from the Indian Ocean. Of course, in the 

 present state of our knowledge, the only definite conclusion to be drawn from this is that 



' Bronn's Klass. u. Ordnung. d. Thierrichs, Porifera, p. 447. 

 ^ Bronn's Klass. u. Ordnung. d. Thierreichs, Porifera, p. 353. 



' Perhaps we ought to except the genera Amjjhilectus and Clathria, though the Antarctic Ocean is about the last 

 place in which we should expect to find the latter. 



