SPONGID.E. 35 



with the first indication of a respiratory apparatus. 

 It would seem also that the nutrient matters con- 

 veyed by the currents to the interior of the canals 

 are there assimilated by the sarcode substance 

 lining the latter, much in the same way that par 

 tides of food are approiDriated by the gelatinous 

 processes of Actinophrys or A'nweba, 



5. Meparative powers. — The reparative 

 powers which many Sponges possess are by no 

 means the least remarkable of their vital pheno- 

 mena. If the substance of the Sponge sustain in- 

 jury by incision or otherwise, the wounded sur- 

 faces will be found, in the majority of instances, 

 after a short time, to have completely healed. It 

 has also been proved that separate fragments be- 

 longing to the same species of Sponge, if placed in 

 contact and allowed to remain undisturbed, will 

 often, within a few hours, unite together, so as to 

 form a single specimen ; and it has been further 

 ascertained that the process of adhesion is in no 

 wise interrupted by suffering the water to drain 

 away from the specimens which are made the sub- 

 ject of experiment. 



6. Spietila. — The spicula or mineral bodies, 

 which are found in the majority of Sponges, vary 

 considerably both in form and size {figs, 6 and 7). 

 They occur throughout all the various structures 

 of the animal, each of whose parts is stated by 

 Dr. Bowerbank to contain its appropriate forms 

 of these bodies ; one kind of spicules being found 

 in the skeleton, another in the sarcode substance, 

 whilst others, which project beyond the surface of 

 the Sponge, are presumed to be of use in defending 



D 2 



