AND PHYSIOLOGY OP THE SPONGIAD^.; 801 
interstitial canals and cavities of the sponge. If we trace the course of the inhaled fluids, 
we find that on their entrance through the pores they are first brought into contact with 
the parietes of the intermarginal cavities, and passed thence into the complicated system 
of digestive surfaces which line the incurrent and excurrent canals and cavities of the 
sponge, and that the exhausted fluids charged with faecal matters are finally discharged 
without the slightest return to or intermixture with the contents of the intermarginal 
cavities. We may therefore, it appears to me, safely conclude that the respiratory and 
digestive functions are separated, and that the latter has its seat in the intermarginal 
ca^ities, and the former in the interstitial canals and cavities. 
The vital energy of the Spongiadge must be very considerable, and the quantity of 
oxygen consumed by their respiration great, if we may judge by the effects of their pre- 
sence in the vivarium, where their introduction makes sad havoc among the other inha- 
bitants, few being able to withstand theu’ deleterious presence, and without a large 
supply of water and a frequent change of it they themselves quickly expire of exhaustion. 
JSutrition. 
In treating on the subjects of inhalation and exhalation, I have described the energetic 
period of action in the sponge during the imbibition of the surrounding fluid as equiva- 
lent to the operation of feeding in the higher classes of animals. And in my “ Further 
Eeport on the Vitality of the Spongiadse,” published in the Keports of the British Asso- 
ciation for 1857, p. 121, I have described the results of feeding a small specimen of 
Spongilla fluviatilis with finely comminuted indigo in water, and I have there stated that 
“ many of the molecules might be readily followed, as they meandered through the 
interior of the sponge, and were seen flowing in every direction. During the mainte- 
nance of this action in full force, when I directed my observation to the osculum, it was 
pouring forth a continuous stream of water, and along with it masses of flocculent 
matter, and many of the larger molecules of the indigo that had entered by the pores ; 
but it is remarkable that although the finer molecules of indigo were being imbibed by 
the pores in very considerable numbers, very few indeed of them were ejected from the 
osculum ; and if the imbibition of the molecules continue for half an hour or an hour, 
and then cease, the sponge is seen to be very strongly tinted with the blue colour of the 
indigo, and it remains so for 12 or 18 hours, after which period it resumes its pellucid 
appearance, the whole of the imbibed molecules having undergone digestion in the 
sarcode lining the interior of the sponge, and the effete matter having been ejected 
through the osculum.” If we kill the sponge immediately after being thus fed, and 
examine the interstitial canals and cavities, we find their sarcodous surfaces thickly 
dotted with molecules of indigo. 
The fsecal matters discharged by the oscula exhibit all the characteristics of having 
undergone a complete digestion ; whatever may have been the condition of molecules of 
organized matter when they entered the sponge, their appearance after their ejection is 
always that of a state of thorough exhaustion and collapse. 
