SPONGES AND ANIMALCULES 



765 



of flinty fibres that may be over a foot in height. 

 One of the compound or social sea-anemones is in 

 the habit of forming bark-like encrustations on this 

 glassy stem, and it was for a long time doubtful whether 

 the sea-anemone or the sponge produced the support- 

 ing-stalk. 



The ANIMALCULES, which represent the simplest 

 and lowest forms of living animals, consist chiefly of 

 organisms which are the equivalents of one of the 

 single cells, or, as they might be termed, the 

 "life-bricks," out of which all the higher animals, 

 and also plants, are built up. They are of minute 

 dimensions, and require the aid of the microscope 

 for their proper investigation. Among the most 

 highly organised members of this sub-kingdom 

 mention must be made of the CILIATED ANIMALCULES, 



or INFU- 



SORIA, 



socalled 



because 



they 



were 



first dis- 



covered 



inhabit- 



in g d e- 



caying 



vege- 



table 



and ani- 



mal in- 



fusions. 



The so- 



called 



SLIPPER-ANIMALCULE is one of the commonest 



forms which makes its appearance amidst such 



environments. The length of this single-celled 



animal scarcely averages the one-hundredth part 



of an inch, but within this restricted space an 



amazing degree of structural and functional 



differentiation is included. Its outer surface 



is, in the first place, densely clothed with hairs, 



which represent its organs of locomotion. This 



outer cell-wall has a subjacent somewhat softer 



layer, in which are developed as crowded a series 



(as compared with the hairs) of minute rod-like 



bodies, which, under various stimuli, can be shot 



out like darts through the skin, and are adjudged 



to be offensive and defensive weapons, partaking 



much of the same nature as the thread- or 



stinging-cells of sea-anemones. Among other 



noteworthy Structures, the slipper-animalcule 



Photo b) W. Saviltt-Kint, F.Z.S.'] [Milfard-n-Sta 



PORTUGUESE BIRD'S-NEST SPONGE 



Dredged from a depth of 600 fathoms off the coast of 



Portugal. In life the body, or "cup," of this 



sponge -was deep orange colour, from 'which 



the grey beard-like mass of anchoring 



fbres depended 



Ltnards 



ph>t, by E. connoW] 



CHALINA SPONGE 



Composed partly of horny and partly of flinty clement* 



