G2 bull?:tin of the 



Tlie Manicina areolata (Plate III.) shows also a very rapid rate of 

 increase. This coiTesponds to the rate of growth of allied genera. 

 [M<xandrina labyrinthica) observed by Pourtales at Fort Jefferson, 

 Tortugas. 



The Isophyllia dipsacea (Plate IV.) shows a still more rapid increase. 



Of course, we are unable to state that these corals began to grow the 

 first season the cable was laid ; but, judging from the favorable locality 

 in which the corals were found, it is not probable that more than a few 

 months passed before some of the swarms of pelagic coral embryos which 

 must have floated past the cable found a place of attachment. 



The specimens have all been figured of the natural size. 



The figures all show, with the exception of those of Manicina, the 

 size of the cable to which the corals were attached. 



Cambridge, August, 1890. 



