118 



LOWER INVERTEBRATES. 



smaller there they have in all important respects a similar structure to the terminal 

 individual. 



The branch of Madrepore, when alive, presents an 

 altogether different appearance from that which the 

 Meached skeleton has. By carefully studying the soft 

 portions of a growing coral of this genus, it will be 

 noticed that the terminal and lateral individuals have 

 the general appearance, as far as their soft tissues are 

 concerned, of a minute searanemone or a typical Acti- 

 nozoan. Each individual has a brownish, cylindrical 

 body, composed for the most part of water, with a 

 central stomach, into which opens a mouth at the free 

 end of the animal. 



In the species which we are now considering, the 

 less conspicuous bodies, which arise from all sides of 

 the calcareous branch upon which they are formed, 

 originate as buds from the base of the terminal indi- 

 vidual. In order to understand the relationships 

 between the large terminal and the smaller lateral 

 individuals, both of which form a colony in the branch 

 of a Madrepore, we must regard the former as a parent 

 form from which all the lateral have budded, and of 

 which they are the young. Suppose that we go back 

 in the development of the branch to a time when there 

 was but one individual where now we find a branch 

 with the colony clinging to its sides. At that time 

 there would be formed a small, single individual, bear- 

 ing every likeness to that whicli is now terminally situated on the branch. As growth 

 goes on from that early condition, buds arise one after another from its base and sides 

 in a manner identical with that which we find in 

 the genus Metridium, which we have already 

 described. As the coral with its attached bud 

 at the base grows, there is deposited near its 

 attachment a larger amount of lime than is nec- 

 essary, so that in fact the processes of life are 

 impeded by the surplus of solid matter in the 

 tissues. The result is that the lower part of 

 the animal becomes dead matter, while at the 

 same time the soft portion of the same is grow- 

 ing upward, and is rising above the solid matter, 

 now too much solidified to allow vital processes 

 to go on in that portion of the Madrepore. The 

 original animal, however, still lives, and its place 

 is not wholly taken by the buds which earlier 

 in its history formed upon it. A surplus of solid deposition in the walls of the base 

 of the bud cements it firmly to the parent, while from the live part of the original 

 polyp, now slightly elevated above the plane in which it formerly was, there forms a 

 second bud, a third, a fourth, and so on. A repetition of the formation of too much 



Fig. 109. — Madrepora verrucosa. 



Pig. 110. - 



■ Section of Madreposa verrucosa, 

 enlarged. 



