. FIG. 2.—POCILLOPORA GROWTH VARIETIES. where it never occurs. Toward the shore colonies become fewer and fewer with many gaps between, and it is found by experiment that they belong to the hardy species, which will stand exposure to over- heating of the shallow water by the sun and suspended mud or sand from the adjacent shore. These, like some species of Poriks, are very different, in this respect, from the more delicate corals of the middle region and reef edge. Some genera are distributed widely over the breadth of the reef, and in this case there are several species replacing each other,
. FIG. 2.—POCILLOPORA GROWTH VARIETIES. where it never occurs. Toward the shore colonies become fewer and fewer with many gaps between, and it is found by experiment that they belong to the hardy species, which will stand exposure to over- heating of the shallow water by the sun and suspended mud or sand from the adjacent shore. These, like some species of Poriks, are very different, in this respect, from the more delicate corals of the middle region and reef edge. Some genera are distributed widely over the breadth of the reef, and in this case there are several species replacing each other, or, as in the genus Pocillopora, one very variable species. The photo- graph here given (Fig. 2) illustrates a colony with massive branches from the reef edge, and a looser delicately branching one from the quieter waters toward the shore, but both belonging to this species. Even more interesting than the correspondence to position is the effect produced in Pocillopora by a small crab (Hapalocarcinus) which associates itself with the coral particularly. The female, which attains the size of a pea, settles down between two growing buds and controls their growth by the current of water she sends out from her gill chambers. The two buds broaden out to short palmate branches, quite unlike the ordin- ary slender forms, and curve over and unite to form a closed chamber about the size of a hazelnut, with small perforations serving for the passage of water and food, and kept from closing only by the prisoner's respiratory activity. The female crab is fertilised by the much smaller male before the "gall " closes, and sends out her numerous offspring through the pores. But, though the form of these curious structures reminds one strongly of vegetable "galls," yet there is no exact parallel between the two cases, for the crab works by directing the growth of the coral rather than stimulating the tissues to abnormal activity. Experimental work on the growth of coral c
Size: 3232px × 1547px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookleafnumber190, booksponsoruniversityofto, booksubjectscience
