GREAT WATER NEWT. 143 



If a plant with long leaves be thrown into a pool where there 

 are tritons, for only a single night during the breeding season, 

 it will be found on the following morning to have a number of 

 its leaves folded, and within each fold an ovum.* 



When it is first deposited, the ovum or egg is of a 

 globular shape, with a little white yolk in its centre, 

 floating in a watery fluid, and surrounded by a 

 delicate but firm transparent shell or capsule. This 

 latter is covered on the outside with a gelatinous 

 adhesive substance, which assists in securing the 

 ovum to the leaf within which it is folded. If the 

 egg becomes exposed too early to the full influence 

 of the water, it is addled or rendered sterile. 

 Within about fourteen days they become so large as 

 to force the folds of the leaf apart, and expose them- 

 selves to the water, which at that period exerts no 

 deleterious influence. From a series of experiments 

 instituted by Mr. Higginbottom, it is clear that 

 constant counter-currents are going on, of water 

 passing into and out of the cell of the ova 4 through 

 their transparent walls. This is doubtless necessary 

 at the present stage for the perfect development of 

 the eggs. At the end of three weeks the embryo is 

 fully formed, moves freely within its envelope, and 

 shortly escapes. External circumstances, especially 

 temperature, exert considerable influence upon the 

 growth of the embryo, and either hasten or retard 



* Higginbottom, in " Ann. Nat. Hist.," 2nd ser. XII., p. 371. 



