SPONGILLA. 157 



diaphanous pellicle which invests the soft jelly of the sponge and 

 its canals had a general resemblance to the cuticle of the leaves 

 of many of our common plants ; while the jelly itself is very si- 

 milar to their parenchymatous substance, composed as it is of 

 numerous pellucid globules. It was ascertained also that the 

 green colouring matter or " chromule" contained in these glo- 

 bules, on being pressed out, gave a permanent green or yellow- 

 ish-green colour to white paper, not to be distinguished from 

 the stains produced by the chromule of leaves and plants ; and 

 strong acids had the same effects on the sponge as they are seen 

 to have upon plants macerated in them. Add to these corre- 

 spondencies the fact that numerous bubbles of gas, most proba- 

 bly oxygen, are disengaged from the surface of the living mass 

 of Spongilla, when exposed to the brightest solar light, just as 

 is knowii to occur with the leaves of a plant when immersed in 

 water and submitted to the direct action of the light of the sun, 

 and we have seemingly a series of proofs which, in the absence 

 of any trace of animal organization or property, almost demon- 

 strate its sameness with the products of vegetable life. 



In whatever way this question may be settled, it is now indis- 

 putable that the verdict affects the position and rank, not of the 

 Spongilla alone, but of the whole family of sponges ; and there 

 are facts which this wider range of the enquiry brings before 

 us, that makes us hesitate to accept the proofs of Mr Hogg as 

 valid and complete. The anomalous circulation through the 

 sponge is one of these facts, for its existence in every species, 

 and the sameness of its phenomena in all, are surely incompa- 

 tible with the explanation of it which Mr Hogg has given. Af- 

 ter many careful experiments, my friend asserts that he has 

 never been able to witness these currents in any specimen of 

 Spongilla which has been entirely destitute of every parasitical 

 insect or other animal ; and he has therefore concluded that the 

 currents are caused by some insect, (usually by the anomalous 



