OF THE SPONGIADJE. 93 



are flowing, bearing with them the molecules of animal or 

 vegetable matter that are floating in the surrounding water, 

 and in small specimens of SpongiUa the molecules, thus 

 imbibed by the pores, may be seen rapidly traversing the 

 tortuous canals of the sponge, being frequently suddenly 

 arrested in their course, and adhering to the sarcodous sur- 

 face over which they are gliding ; and if, while the rapid 

 inhalent process is going on, and an infinite number of 

 extraneous particles of matter are seen entering the pores 

 in every direction, we turn our attention to the excurrent 

 streams from the oscula, we shall be at once struck with 

 the comparatively small number of effete particles that 

 issue from those orifices. While on the contrary, if we 

 examine the oscula while the gentle breathing inhalation 

 only is proceeding and the nutrient particles are rarely 

 seen entering the pores we shall not fail to observe that 

 the amount of effete particles ejected from the oscula is 

 still continuing with a regularity that is strikingly indi- 

 cative of their systematic and gradual liberation from the 

 sarcodous surfaces of the interior of the animal, and it may 

 be further observed that the molecules thus ejected are 

 very much below the average size of those previously 

 imbibed, and that they are always in an exhausted and 

 collapsed condition. 



If sections of a sponge in a living state be examined by 

 transmitted light with a power of about 500 or 600 linear, 

 the whole of the sarcodous substance will be seen abound- 

 ing in the nutrient particles, some simply adhering to the 

 surface, while others are embedded at different degrees of 

 depths, exhibiting all the varieties of form and condition 

 that are so characteristic in the molecules described as 

 existing in the mucous lining of the intestine of the mouse, 

 and in many cases, excepting that in the Spongiadas, the 

 sarcodous surfaces are somewhat more evenly spread over 

 the membranes on which they repose ; such is their simi- 

 larity, that the two tissues, so distant from each other in 

 the scale of created beings, can scarcely be distinguished 

 from each other under the microscope. 



There are other points of similarity existing between the 



