CHAPTER II 



THE SPONGES 



FOR a long time the Sponges, or Porifera, were a great puzzle 

 to naturalists, and were bandied about from the animal to the 

 vegetable kingdom and back again. Thus we find Aristotle con- 

 cluding that they were lowly forms of animal life bearing a certain 

 resemblance to plants ; while old Gerard, writing in the sixteenth 

 century in his famous " Herbal," would have us believe them 

 formed of " a certain matter wrought together of the foame or 

 froth of the sea." So late as the middle of the eighteenth century 

 it was suggested that Sponges were really formed by certain marine 

 worms as shelters from their foes, the spongy mass being " merely 

 a nidus or secretion." This was contradicted by Ellis (1765), 

 who, in the course of his examination of a living Sponge, " plainly 

 perceived the small tubes inspire and expire," and concluded that 

 the " openings of the branched tubes are the mouths by which 

 it receives its nourishment and discharges its excrements." 



It was not until after the fundamental discoveries of Robert 

 Grant, in 1825, that the right of the Sponges to a place in the 

 animal kingdom was universally admitted. Even then they 

 were at first relegated to the Protozoa, and from the discovery of 

 the resemblance of their collared-cells to the flagellate Infusoria, 

 were for some time regarded as mere aggregates of those Pro- 

 tozoa. Since then, however, the very precise and thorough in- 

 vestigations which have been carried out concerning the structure 

 and embryology of the Sponges has left little doubt as to their real 

 character as primitive Metazoa or multicellular animals. 



Marking, as it does, an epoch in the scientific investigation 

 of the Sponges, Grant's own account of his earliest observations 

 is of the greatest interest : " In the month of November last," 

 he writes, " I therefore put a small branch of the Spongia coalita, 

 with some sea-water, into a watch-glass, under the microscope 



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