THE VICTORIAN NATURALIST. 191 



plex forms of the Heterocoelans, represented by Leucandra 

 echinata and Leucilla Australiensis — not the least interesting 

 amongst the Heterocoelans being the stalked form known as Si/con 

 raphanus. This is a splendid type of a calcareous sponge for 

 the microscopist, the perfect sponge being of such a small size 

 that it can be mounted whole for examination under a low power. 

 Indeed, all the sponges referred to above are fairly minute, and if 

 placed in sea-water can be kept alive for a considerable time, 

 thus affording a ready means of examining some points in the 

 anatomy of the group. For instance, if one of the stalked 

 varieties is placed in sea-water under a low power of the micro- 

 scope, the inhalent and exhalent currents can be clearly seen — 

 the currents being rendered more conspicuous by the addition of 

 a few grains of powdered carmine to the water containing the 

 living sponge. If killed and prepared for microscopic work many 

 interesting details can be made out, not only in the sponge 

 mounted as a whole, but by means of thin slices cut with an 

 ordinary razor and mounted in balsam. On the present occasion 

 many of the sponges were placed at once into different media,, 

 such as absolute alcohol, Kleinenberg's solution of picric acid, 

 and a one per cent, solution of osmic acid. Judging from some 

 preparations made by Mr. Shepherd from material killed by osmic 

 acid that method proves to be of the greatest value in histological 

 work, the shape and structure of the collared cells lining the 

 flagellate chambers being very clearly defined. Further investi- 

 gations on specimens killed by this method will, doubtless, tend 

 to clear up some of the doubtful points which exist as to the 

 extent and function of SoUas's membrane. I have also a series 

 of sections of a sponge (Si/con raphanus) collected here, which 

 shows nearly all the principal stages in the development of a 

 calcareous sponge, and the fact is referred to as proof to members 

 that plenty of material is within easy reach for working out the 

 development and anatomy of one of the most interesting groups 

 in the animal kingdom. 



The calcareous sponges, however, do not nearly monopolize all 

 the space in this particular spot, for we find, living side by side 

 with them, various species of both silicious and horny sponges. 

 Indeed, the under surface of many stones is entirely covered 

 over with a very delicate film, which examination shows to be 

 the substance of a silicious sponge, and dotted over it here and 

 there are tiny upward growths, which prove to be calcareous 

 sponges. Scrape some of the thin film carefully from the stone 

 and place it in spirit, in which it will keep till such time as it can 

 be prepared as a " mount " for examination. It is worth all the 

 trouble, for the microscope will show it to be made up of a mass 

 of protoplasm, in which is embedded thousands of very delicate 

 " pin-headed " spicules, typical of some of the silicious sponges. 



