EARLY LIFE-HISTORY OF CORALS 63 



times it has been noticed tliat many colonies are ripe and are 

 actively giving rise to embryos, whilst at other times no 

 actively reproducing colonies can be collected. 



The early stages of the young coral will be described but 

 briefly, and only such details given as are necessary to make 

 clear the manner of its life, and the manner of its attaining its 

 adult condition. 



The ova and spermaria are developed from the epithe- 

 lium that covers the mesenteries within the body of the 

 parent zooid : some differences in their distribution occur in 

 different species, for in some cases only ova are found and in 

 some only spermaria. AVhen both elements occur together 

 they may be developed separately on different mesenteries 

 within the same zooid, or they may both be present on the 

 same mesentery ; any mesentery may be the site of develop- 

 ment of ova and spermaria, but the ova always tend to be 

 developed at the attached radial edge, and the spermaria at 

 the free central margin. "When mature, the reproductive 

 elements are passed from the central cavity of the zooid along 

 the stomodeum, and through the mouth out into the water, 

 the passage being effected by jerking movements of the parent 

 zooid. 



The stage of development, in Avhich the rejoroductive 

 elements are liberated, varies considerably, for Avhile some 

 observers have seen the male cells and female cells extruded 

 individually in the process of spawning, still it appears to be 

 a more general rule that viviparous reproduction is adhered 

 to, and a young embryo is extruded into the water. The 

 segmentation of the ovum, and the early stages of the 

 development of the larva, take place, as a rule, within the 

 internal cavity of the zooid, and the larvae are shot out 

 through the mouth in successive -batches. In Manidana 

 areolata, Duerden observed that a dozen or more larvse were 

 ejected at a time, whilst in Forites davaria, Favia fragum, and 

 Siderastrcea radians, they came out singly or in twos and threes. 

 As the process of spawning advances, and as more and more 

 batches are ejected, the stage of development of the extruded 



