THE VICTORIAN NATURALIST. 65 



viz., Metazoa, or many-celled animals, has been definitely estab- 

 lished. We shall be able, with the abundant material at our 

 disposal, and with the aid of a strong magnifying glass, a glass 

 tumbler, a sharp razor, a deep watch-glass, and a little patient 

 watching, to discover some of the facts upon which their present 

 classification is based. 



One of the most convenient forms to take for examination will 

 be a specimen of the cylindrical variety belonging to the family 

 Syconidce. These forms are found attached to the under surface 

 of loose stones, and are usually about i inch in length, and 

 yellowish-brown in colour. They can easily be detached from 

 the stone by the point of a knife, and transferred to a vessel con- 

 taining salt water. Sometimes they attach themselves to pieces 

 of sea-weed, and in this case the weed and sponge can be trans- 

 ferred together to the vessel, thus affording a better opportunity 

 for examination than if separated from its support. On reaching 

 home, transfer the sponge to a watch-glass or shallow glass vessel, 

 so that it is well within focus of the hand lens, and after the sponge 

 has become accustomed to its new surroundings a current of water 

 will be seen issuing from the top of it. This will be the more 

 evident if a pinch of powdered carmine is added to the water, and 

 as the current is fairly constant hour after hour, it is evident that 

 its source must be constant too. If the hand lens is powerful 

 enough smaller currents will be seen setting in towards the 

 sides of the sponge and these form the source of supply to the 

 larger current. The actual course taken by the current is not 

 very evident, however, till we remove the sponge from the water, 

 and with a sharp razor make a longitudinal cut through the very 

 centre of it. This reveals the fact of a central cavity, the gastral 

 cavity, extending from the bottom to the top of the sponge, the 

 cavity being closed at the bottom and open at the top. Another 

 fact, not quite so evident, however, can be made out, namely, 

 that there are tiny breaks in the continuity of the wall which lead 

 into minute open spaces. This rough-and-ready method of exam- 

 ination will not furnish much information about the actual 

 direction of the current, but more exact work with proper ap 

 pliances reveals much more, and we are able to trace, step by 

 step, the exact course of the stream of water through the 

 tiny openings or pores in the skin of the sponge to the central 

 cavity — in fact, to establish a definite canal-system which may 

 be regarded as the circulatory system, commencing at the 

 pores and ending at the outlet at the top of the sponge 

 through what is known as the osculum. In man the circulatory 

 system is a closed one, in the sponge it is open ; in man oxygen 

 and nutrient material are carried to every part and parcel of the 

 body by means of the circulatory system ; in the sponge the sea 

 water courses through the canal-system, carrying not only the 



