SPONGES COLLECTED IN SCOTLAND. 247 



generation. It is by no means improbable that someone will some day 

 evolve a system of classification such as that foreshadowed in Bernard's 

 " Catalogue of the Madreporarian Corals in the collection of the British 

 Museum " as regards Porites, in which species are no longer recognized. 

 At present, at any rate by museum zoologists, generic and specific names 

 cannot be ignored, for no satisfactory substitute for them has yet been 

 proposed. 



The specimens of S. lacustris from Edinburgh may be taken to represent 

 the typical form of the species, but even they are not absolutely identical 

 inter se ; some of them have no branches, while in others these structures 

 are well developed, as is usually the case in British specimens. In the 

 branchless examples the skeleton spicules are rather shorter than in 

 the others. In the branched examples the gemmules are abundant, being 

 young and imperfectly developed towards the distal end of the branches, 

 but fully formed at their bases and in the flat part of the sponge. There 

 are no gemmules in the specimens without branches, which are probably 

 immature. 



The specimen from the River Dee encrusts the stem of a water-weed 

 and is devoid of branches. It contains a few gemmules of unusually 

 large size, but apparently still immature, the internal coat being very soft 

 and as yet having few spicules and no crust associated with it. The 

 skeleton in this form is rather more coherent than usual, but cannot be 

 compared in this respect with that of S. alha, which is hard to the touch. 



I have refrained from giving measurement of the spicules or gemmules 

 so far, because I believe that measurements of these structures in the 

 more variable species of Sj^ongilla are apt to lead to confusion by being 

 taken as standards of comparison ; there is nothing really remarkable 

 as regards them either in the specimens from Edinburgh or in that from 

 the River Dee. 



The third Scottish form I have examined is altogether more abnormal. 

 I found it in considerable abundance on the lower surface of stones near 

 the edge of Loch Baa in the island of Mull. Several of my specimens 

 had evidently attained their full growth, being practically dead and 

 consisting merely of skeletons to which a few cells still adhered. Not- 

 withstanding their abundance, however, no specimen measured as much 

 as 10 mm. in diameter ; there was no trace of branches, each sponge 

 consisting of a little mound-shaped structure of oval outline and having 

 a single osculum of relatively large size. The gemmules, although they 

 •were fully formed, bore no spicules, and the flesh-spicules were very few, 

 occurring only in the substance of the sponge. The colour, considering 

 the conditions under which the sponges were growing, was normal, being 

 a dirty cream where they were shut off from light and a faint green where 



