. The Cambridge natural history. Zoology. PHYSIOLOGY DISTRIBUTION 239 lip the strands of spicules as they formed them, leaving the lower parts behind and adding to the upper ends. , Of the physiology of the pigments of sponges not much is yet known: a useful summary of facts will be found in Von Fiirth's text-book.'' Spongin.—Von Fiirth ^ points out that this term is really a collective one, seeing that the identity of the organic skeletal substance of all sponge species is hardly to be assumed. Spongin is remarkable for containing iodine. The amount of iodine present in different sponges vari
. The Cambridge natural history. Zoology. PHYSIOLOGY DISTRIBUTION 239 lip the strands of spicules as they formed them, leaving the lower parts behind and adding to the upper ends. , Of the physiology of the pigments of sponges not much is yet known: a useful summary of facts will be found in Von Fiirth's text-book.'' Spongin.—Von Fiirth ^ points out that this term is really a collective one, seeing that the identity of the organic skeletal substance of all sponge species is hardly to be assumed. Spongin is remarkable for containing iodine. The amount of iodine present in different sponges varies widely, reaching in certain tropical species of the Aplysinidae and Spongidae the high figure 8 to 14 per cent. Seaweeds which are specially rich in iodine contain only 1'5 to 1'6 per cent. In view of the fact that iodine is a specific for croup, it is of interest to observe that the old herb doctors for many centuries recognised the bath sponge as a cure for that disease. Distribution in Space.—All the larger groups of Sponges are cosmopolitan. Each group has, however, its characteristic bathy- metrical range : the facts are best displayed by means of curves, as in Pig. 122, which is based wholly on the results obtained by the " Challenger" Expedition. The in- formation as to littoral species is con- sequently inadequate, and we have not the data requisite for their discussion. Sponges generally (a) and Monaxonida in particular (b) are more generally dis- tributed in water of depths of 51 to 200 fathoms than in depths of less than 50 fathoms; but localities in shallow water are 1 Fergl. Physiologie d. niederen Thiere, I. FiQ. 122.—The ordinals mea- sure (i.) the number of species, a-/, and (ii.) the number of stations, a'-f, at which successful hauls were made. The abscissae measure the depth : thus at I. the depth is from 0 to 50 fathoms ; at IE. from 51 to 200 ; at III. from 201 to 1000 ; at IV. froni 1001 upwards, a,a, are the curves for Sponges gene
Size: 884px × 2827px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
