PORITES. 17 



Another somewhat striking case is supplied by those forms which swell as they rise. Of 

 these there is one minute egg- or pear-shaped initial growth * which has not yet begun to show 

 signs of forking, and several adult stocks. These adult stocks can be seen to have the same 

 character throughout. The forking is as nearly as possible at the same angle, usually very 

 small ; the stems steadily thicken, their tips swelling and dividing mostly into rounded knobs, 

 the forking becoming more and more irregular as the fusions increase in number. But as they all 

 rise from very small bases they must apparently all sooner or later tumble over unless the great 

 lateral expansion of the whole practically forms a new support sufficient at least to keep it 

 from falling far. PI. XVI. fig 1, is a sample of such a growth. PL XIV. fig. 5 is another with 

 very irregularly thickening stems. PI. X. fig. 2 shows another on a very small scale. P. Porto 

 Rico 3 figured by Dr. Vaughan appears to show the same (see further Table III., E. d. p. 136). 



In passing, and in connection with these forms, which swell at once above a minute base, 

 I should like to call attention to the one figured by Duchassaing and Michelotti, and called by 

 them " P. macrocephala " (see p. 89). Though the figure shows some irregularity in the style 

 of upward growth, one portion, at any rate, swells into a blunt inverted cone, which appears to 

 have suggested the original name. Wldle it is doubtful whether this is normal, there is little 

 doubt that such forms might well be developed as an extreme of such forms as those shown on 

 PL XI. figs. 4 and 5, which are further illustrations of stocks built by a repetition of swelling, 

 pear-shaped up-growths. 



Now these cases appear to show that the principle of growth, described above as 

 apparently applicable to the massive explanate forms, is true for the different kinds of 

 branching stocks as well. Only we now gather that each joint of a branching Pontes is as 

 nearly as possible a repetition of the original stem, that is practically of the initial colony 

 minus its basal disk (which is no longer necessary), and repeats its height, its method of division, 

 and its angle of forking. 



In the absence of such direct proof as we might have obtained from a large series of 

 growing stages, we call attention to the fact that in no form is the branching wild and variable ; 

 the character of each form is always true tliroughout whether it is large or small. Further, a 

 point of special interest is the fact that the stems between successive forkings frequently vary 

 in thickness (e.g. P. Curaqoa 1). There seems, as a rule, to be very little gradual thinning away 

 of the dichotomously branching stems from below upwards, which there would be if the whole 

 were a complete unit of growth. The terminals are often almost as thick as the adult portions, 

 and any particular forking section may be even somewhat thicker than the initial stem, or, what 

 is the same thing, than any one below it. This suggests that each such section is a repetition 

 of the initial or basal stem, some a little better nourished, some a little worse. 



If this is true of the West Indian Porites as a fundamental growth principle, it is difficult to 

 believe that it is confined to the West Indian forms alone ; one would expect it to be universal. 

 As a matter of fact it was only suggested by one of the Indo-Pacific forms, P. Ceylon, 4., see 

 Vol. V. p. 266 ; although it is probable that if the series could be worked over again it would 



• P. Barbados 10, p. 42. 



