SPONGIDA. 67 
satisfied of the animal nature of sponges, although they once were 
thought to represent the lowest and most obscure grade of animal 
existence, and that so close to the confines of the vegetable world, 
that it was considered difficult in some species to determine whether 
they were on the one side or the other. “Several of them, however,” 
says Mr. Gosse, “if viewed with a lens under water while in a living 
state, display vigorous currents constantly pouring forth from certain 
orifices ; and we necessarily infer that the water thus ejected must be 
constantly taken in through some other channel. On tearing the 
mass open, we see’ that the whole substance is perforated in all 
directions by irregular canals, leading into each other, of which some 
are slender, and communicate with the surface by minute but 
numerous pores, and others are wide, and open by ample orifices ; 
through the former the water is admitted, through the latter it is 
ejected.” 
The physiological function of the tubes and orifices which 
present themselves on all parts of the sponge has been interpreted in 
various ways. Ellis, writing in 1765, supposes that they were the 
orifices of the cells occupied by the polypes. In 1816 Lamarck still 
advocated this opinion; and even now we find the observer whose 
notes M. Frédol has edited with so much judgment asserting that 
‘“‘the inhabitants of the sponge are a species of fleeting, transparent, 
gelatinous tubes, susceptible of extension and contraction; young 
polypes, as we may call them, without consistence, without cilia ; 
incipient polypes, in short, of very simple but sufficient organisation. 
The animalcule of the sponge is a stomach, without arms, very 
simple, very elementary—in short, an animal all stomach !” 
This mode of considering the sponge is not conformable to the 
views of the leaders of modern science. Professor Milne-Edwards, 
for instance, in place of seeing in the sponge a collection of united 
beings, forming as it were a colony, considers each to be an isolated 
being, a unique individual. The innumerable canals by which the 
sponge is traversed, according to that author, are at once its digestive 
organs and breathing pores. The vibratile cilia are necessary to the 
renewed aération of the water required as a respiratory duid in the 
interior canals of the sponge. The currents in these channels have 
one constant direction. The water penetrates the sponge by nu- 
merous orifices of minute dimensions and irregular disposition ; it 
traverses channels in the body of the mass, and finally makes its 
escape by special openings. According to this view, the channels of 
the sponge perform the two functions of digestion and respiration. 
The rapid currents of aérated water which traverse them lead into 
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