144 OUR REPTILES. 



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

 there are tritons, for only a single night during the breed- 

 ing 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 sur- 

 rounded 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 themselves 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, 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 circum- 



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

 371. 



