116 CRITIQUES AND ADDRESSES. [vi. 



the commoner white corals, each polype has a complete 

 skeleton of its own. These polypes ate sometimes soli- 

 tary, in which case the whole skeleton is represented by 

 a single cup, with partitions radiating from its centre 

 to its circumference. When the polypes formed by bud- 

 ding or division remain associated, the polypidom is some- 

 times made up of nothing but an aggregation of these 

 cups, while at other times the cups are at once separated 

 and held together, by an intermediate substance, which 

 represents the branches of the red coral. The red coral 

 polype again is a comparatively rare animal, inhabiting 

 a limited area, the skeleton of which has but a very 

 insignificant mass ; while the white corals are very com- 

 mon, occur in almost all seas, and form skeletons which 

 are sometimes extremely massive. 



With a very few exceptions, both the red and the 

 white coral polypes are, in their adult state, firmly ad- 

 herent to the sea-bottom ; nor do their buds naturally 

 become detached and locomotive. But, in addition to 

 budding and division, these creatures possess the more 

 ordinary methods of multiplication ; and, at particular 

 seasons, they give rise to numerous eggs of minute size. 

 Within these eggs the young are formed, and they leave 

 the egg in a condition which has no sort of resemblance 

 to the perfect animal. It is, in fact, a minute oval body, 

 many hundred times smaller than the full-grown crea- 

 ture, and it swims about <with great activity by the help 

 of multitudes of little hair-like filaments, called cilia, with 

 which its body is covered. These cilia all lash the water 

 in one direction, and so drive the little body along as 

 if it were propelled by thousands of extremely minute 

 paddles. After enjoying its freedom for a longer or 

 shorter time, and being carried either by the force of its 

 own cilia, or by currents which bear it along, the embryo 

 coral settles down to the bottom, loses its cilia, and 



