PHYSIOLOGY OF THE SPONGE: GRANT'S DISCOVERY. 



313 



certainly even whether they should regard the Sponge as an animal or a plant. Some, like Lamarck, 

 supplied what was wanting by a free use of the imagination, and, supposing that the oscules were the 

 mouths of cells occupied by little polypes, which constantly succeeded in evading observation, were enabled 

 to class the Sponges with the Alcyonia ; while some zoologists, who knew little about plants, handed 

 over an organism which 

 they did not understand to 

 the care of the botanists. 

 Nor was much help to be 

 had from an examination 

 of the Sponge in a living 

 state ; for, beyond mere 

 growth, it presents no ob- 

 vious signs of life. Mar- 

 sigli was the first, in 1711, 

 to observe the dilatation, 

 and contraction of the 

 oscular openings, and after- 

 wards Ellis asserted that 

 he saw currents of water 

 flow into them as well as 

 out a most exceptional 

 occurrence and thence 

 inferred that the oscules 

 were mouths by which the 

 Sponge sucks in and squirts 

 out water. In all this there 

 was no progress, and it is 

 to Robert Grant that we 

 are indebted for the funda- 

 mental discovery which dis- 

 persed the mystery that 

 had surrounded the physi- 

 ology of the Sponge since 

 the early time of Aristotle. 

 His discovery consisted in 

 the fact that he plainly 

 witnessed currents of water 

 containing floating particles 

 of food flowing through the 

 pores of the skin into the 

 Sponge, and, at the same 

 time, other currents of 

 water, burdened with fecal 

 residues, flowing out of the 

 oscules from the excurrent 

 tubes. By this flow of water 

 through it the life of the 

 Sponge is manifested and 

 maintained. The folio win " 



c> 



is Grant's own account of 

 his earliest observations : 



Kg. 1 SECTION OF TURKEY BATH SPONGE. (After Sclmlze.) 



p.Tore; ,, snbdermal cavity; i.incurrent canal :/, flagrrllated chamber; el, chief fibre of the skeleton : r2. 

 connecting fibres ; o, ova in various stages of growth ; os, ovum segmenting ; m, morula. ( x 40.) 



"Ill the month of November last, I therefore put a small branch of the Spongia coalita, with 

 some sea-water, into a watch-glass, under the microscope, and, on reflecting the light of a candle 



278 



