11G ANATOMY AND PHYSIOLOGY 



bodies. These details by the leamed Professor are so fall 

 and complete as to leave but little room for the improve- 

 ment of our knowledge of this portion of their natural 

 history. And the facts of the imbibition of the surrounding 

 water by the pores in the dermal membrane, its circulation 

 through the internal cavities of the sponge, and its final 

 ejection through the oscula, has been firmly established 

 and acknowledged by all naturalists who have studied 

 these animals closely in a living state. Dr. Grant has, in 

 truth, proved himself to have been, in regard to the aqueous 

 circulation in the sponge, what Harvey was to that of the 

 blood of the higher classes of animal life, the first to dis- 



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cover and to publish the true mode of the circulation of the 

 water in the animal. 



This learned and accurate observer says, " I first placed 

 a thin layer from the surface of the S. papillaris, in a 

 watch-glass with sea-water under the microscope, and on 

 looking at its pores I perceived the floating particles driven 

 with impetuosity through these openings ; they floated with 

 a gentle motion to the margin of the pores, rushed through 

 with a greatly-increased velocity, often striking on the 

 gelatinous networks, and again relented their course when 

 they had passed through the openings. The motions were 

 exactly such as we should expect to be produced by cilia 

 disposed round the inside of the, pores." ' Edinburgh New 

 Philosophical Journal,' vol. ii. p. 127. 



The same author, in describing the excurrent action, 

 says, " The Spongiapanicea (Halichondria incrustans, John- 

 ston) presents the strongest current which I have yet seen." 

 Two entire round portions of this sponge were placed 

 together in a glass of sea-water with their orifices opposite 

 to each other, at the distance of two inches ; they appeared 

 to the naked eye like two living batteries, and soon covered 

 each other with feculent matter. 



Stimulated by the recital of the observations of Dr. 

 Grant, I have often sought these currents flowing; from the 



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oscula, and there is no species in which I have had the 

 opportunity of examining in a fresh and vigorous condition 

 in which I have not succeeded in seeing them. In the 



