OP THE SPONGIAD^. 121 



sad havoc among the other inhabitants, few being able to 

 withstand their deleterious presence, and without a large 

 supply of water and a frequent change of it they them- 

 selves quickly expire of exhaustion. 



NUTRITION. 



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 

 equivalent to the operation of feeding in the higher classes 

 of animals. And in my " Further Report on the Vitality 

 of the Spongiadae," published in the ' Reports of the British 

 Association' for 1857, p. 121, 1 have described the results of 

 feeding a small specimen of 8pongillafluviatilis 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 maintenance 

 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 twelve 

 or eighteen 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 im- 

 mediately after being thus fed, and examine the interstitial 

 canals and cavities, we find their sarcodous surfaces thickly 

 dotted with molecules of indigo. 



