38 THE SPONGES 



geological epoch, down to the present day. Chiefly marine and 

 all aquatic in habit, they have a world- wide distribution, the 

 marine forms inhabiting the seas at all depths, from between tide 

 marks to abysmal depths. Sponges are among the lowest of the 

 multicellular forms of life, occupying a more isolated position 

 than any other group of animals, for they are destitute of multi- 

 cellular relations, though linked by their collared-cells to the 

 colonial Infusorian Protozoa, from which their past history and 

 gradual evolution seem likely to be eventually completely estab- 

 lished. But, to quote such a high authority upon the subject as 

 Professor Minchin, " The most conflicting opinions have been, and 

 still are, held upon this point." On account of their isolated posi- 

 tion, the Sponges or Porifera are placed in, and are the sole repre- 

 sentatives of the Phylum or Sub-Kingdom Parazoa. 



