48 
LIFE, IN ITS LOWER FORMS. 
delicate, could hardly be removed by other creatures. 
Instead, therefore, of being helpless at their birth, the 
young Sponges can, by means of their cilia, row them- 
selves about at pleasure, and enjoy for a period powers of 
locomotion denied to their adult state.”* 
* Outline of Anim. Kingd. IT. 
