SPONGES AND ANIMALCULES 



367 



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- 



fhatt bj W. btvtl.t-Knl, F.Z.S.~\ [Milfsrd-tn-Sit 



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 ivas deep orange colour, from ivhich 



the grey beard-like mass of anchoring 



fibres depended 



M k) E. CnnW] [ S<. Lttnardi 



CHALINA SPONGE 



Composed partly of horny and partly of flinty elements 



S O R I A, 



socalled 

 because 

 they 

 were 

 first dis- 

 covered 

 inhabit- 

 ing de- 

 caying 

 vege- 

 table 

 and ani- 

 mal i n- 

 f u s i o n s. 

 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 



