EVIDENCE FROM COLONIAL OR COMPOUND ANIMALS. 279 



convenient halting-place in our researches into animal individuality 

 and its variations. From forming the bete noire of the naturalist of 

 former years, who was troubled in his mind as to the animal or 

 plant nature of the sponges, to occupying a singular and anomalous 

 position in the animal classifications of to-day, this group of organ- 

 isms has attained a well-merited celebrity. The living parts of a 

 sponge that is to say, the parts which fojm and make the sponge- 

 framework, and which alone concern us in our present investigation 

 consist of masses of protoplasm, which are in their way strictly 

 comparable to the minute bodies, or "cells," of which our own 

 tissues are built up. A sponge, as to its living parts, is a mass of 

 protoplasmic cells, " some of which," as Huxley puts it, " have all 



FIG. 187. SPONGE AND ITS DEVELOPMENT. 



the characters of Amcebcz ; while others are no less similar to monads " 

 these latter being microscopic masses of protoplasm, furnished, 

 like chlamydomonas, with two waving cilia. The comparison of a 

 sponge to a kind of " submarine Venice," with its canals, along the 

 banks of which the inhabitants (or masses of protoplasm) reside, and 

 through which flow the water-currents bringing particles of nourish- 

 ment to these denizens, is therefore seen to be fully justifiable in one 

 sense. Still more justifiable and appropriate would such a metaphor 

 be, could we prove that the sponge was in reality what the simile 

 indicates, namely, a colony of animals seeing that the comparison 

 of the sponge to the Adriatic capital, derives its whole force from the 



