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THE AMEBIC AN NATURALIST [Vol. XLYIII 



relations of individuals. Thus Wood-Jones says of the 

 corals — 



a colony may grow according to five different types of vegetative growth 

 ... it may grow as (1) a spherical mass, (2) an encrusting layer, (3) a 

 free plate, (4) a branching tree-like growth, or (5) a mere amorphous 



He further notes the division of all the corals into two 

 groups of normal growth-forms; for all the zooids may 

 take an equal share in the asexual reproduction or, again, 

 some may be of greater importance than others, and the 

 asexual reproductive functions may be lodged in a very 

 few individuals only. Considering the first division 

 (all zooids taking equal share, the principal types of bud- 

 ding vary from each other in the actual site of origin of 

 the daughter zooid from the parent, in the degree of final 

 separation of the two zooids, and in the thickess of the 

 intervening partition between the two zooids. The 

 amount of rising above the general surface by each indi- 

 vidual zooid is likewise subject to variation. 



Turning now to the corals that constitute the second 

 class (some zooids of greater importance than others) 

 which in the words of Wood-Jones have some of their 

 units specialized as active agents of growth, 

 it is at once seen that the possibilities of variation of normal vegetative 

 habit are greatly increased. All the elaborate branching forms, plates 

 and leaf-like growths belong to this class; and all are evolved by special 

 peculiarities of the growing point. The zooids that constitute the grow- 

 In the first instance, it is necessary !<» draw wry sharp distinctions 

 between two subdivisions of this group. In Group 1 come all those 

 forms like Monti pom, whose distal zooids are the newest formed mem- 

 bers of the colony; and in Group 2 are included the Madrepora, whose 

 distal zooid is the most ancient individual in the whole group. 



In dealing with Group 1 many forms have to be considered, for when 

 the youngest are the active zooids their growth cluster may be variously 

 disposed, and on its disposition the resulting vegetative form entirely 



In Group 2, however, this state of things is entirely altered, for there 

 one zooid, which is situated at the extremity of the stem, and which I 



