"WONDERS OF SPOXGE STRUCTURE. 5 



Without entering into the purely scientific details of 

 sponge-structure, I will endeavour to lay open some of 

 the wonders which are hidden in one of the lowest forms 

 of animal life. 



In order to appreciate the life of a sponge, it will be 

 necessary to examine a living specimen. To procure a 

 living marine sponge is not very easy; but the fresh- 

 water sponges are common enough, and will answer our 

 purpose just as well. They may be procured in almost 

 any slow-flowing river, and are adherent to twigs and 

 similar objects that have remained in the water for some 

 length of time. 



At Oxford I used to find them in the Cherwell and 

 Isis, mostly attached to willoAv twigs that drooped into 

 the water. The still water near a lock is a favourite 

 spot for them, and in sheets of fresh water they are 

 wonderfully numerous. The great Swindon reservoir 

 is so full of them that any amount may be procured in 

 an hour or so. 



Take one of these sponges, the smaller the better, and 

 place it in a glass vessel. A common watch-glass will 

 answer the purpose admirably. Presently, distinct cur- 

 rents will be perceptible in the water, especially if a little 

 carmine or indigo be dissolved in it. Prussian blue is 

 poisonous, but the " blue " used by the laundress is safe 

 enough. Carmine, however, is, in my opinion, better 

 than any blue tint, as it is prettier in general effect, and 

 the particles are so transparent that they do not become 

 opaque when collected together. 



