WEST INDIAN ISLANDS PORITES. 53 



of a long, cylindrical, basal stem, which shows signs of having attempted, in vain, to fork, 

 suggests "that the coral grew in sand, and was consequently only alive at its tips, that is, as 

 hi°h above the shifting medium as possible. Very rapid upward growth would explam its 

 frroility. Further, the fact that his P. recta from an adjoining locality lias the same long dead 

 stalks although by its branching it is a different form, supports this reference of the cause to 

 the nature of the environment : indeed, a sandy bottom is mentioned by Lesueur for that form. 

 These corals ought to be re-discovered, and submitted to a fresh, comparative study, for very 

 little can be ascertained as to the real character of the ultimate forking from the two figures 

 given by Lesueur, excellent as they are. All that we can there gather is that they differ greatly 

 L their initial phases. If the rule holds that the principle of growth in these branching forms 

 is a continual repetition of the initial stages, it is clear that these two forms would make very 

 different adult stocks. See further the observation under P. St. Bartholomew 1, below. 



St. Christopher. 

 From this island Lesueur gathered specimens closely resembling the form he called 

 P. recta, which occurred at St. Bartholomew. 



35. Porites St. Bartholomew 1. (P. Bartolommi prima.) 

 [St. Bartholomew, * coll. Lesueur ; ? ] 

 Syn. Pcnites recta Lesueur, Mem. du Mus. vi. (18-20) p. 288, pi. xvii. fig. 16. 



Description.— The corallum rises on a long, dead, basal stem, some 5 to 6 cm. high, 

 slightly compressed. The tip forks at very wide angles, the terminals being oblique and 

 rounded. The Living layer is confined to the tips of the stems. 



The calicles are small, deep, with spiny or denticulate septa. 



The polyp is of a reddish colour, with white lines running up the body between the 

 tentacles. A white, polygonal, twelve-sided line also runs between the different polyps, 

 apparently following the line of the skeletal walls: perhaps the walls themselves show 

 through. The tips of the tentacles are white, with a semicii-cle of deep bm-nt sienna. 



The coral lives in calm water, and is easily detached from the sandy bottom out of which it 

 seems to grow. 



This Porites, like P. Nevis Island 1, seems adapted to grow out of sand. Note the observa- 

 tions under P. Nevis Island 1, and the confinement of the Uving layer to the summits of the 

 stems. It forks only after it has got some height above the sand. All its growth energies are 

 probably concentrated in the endeavour to rise above the shifting particles which are always 

 injurious to the delicate polyps. Once faii-ly out of the reach of the sand the colony can grow 

 out more freely and begin, however irregularly, to fork in the way characteristic of so many of 

 the West Indian Porites. Lesueur's figures show neither in this case nor in that of P. Nevis 

 Island 1 more than the earliest beginnings of forking. 



Fresh descriptions of these corals are needed with a closer comparison of the calicles. It 



* Lesueur adds also St. Christopher. 



