452 



THE NATURE BOOK 



7 



SOME EARLY STAGES IN THE EVOLUTION OF THE NEWT. 



1, Stalk of Vernal Starwort holding four Newt's eSgs with the leaves bent back 



over them. 



2, An early staSe in the development of the Tadpole within the egg. 



3, A later stage, the tail now plainly visible. 



4, Tadpole immediately after hatching ; one still in the egg above it. 



5, Dorsal view of Tadpole immediately after hatching. 



6, Tadpoles two days old, the eyes and gills now evident. 



7, Ventral view of Tadpole two days old ; one still in the egg on the right of it. 



which permits of its 

 being examined by 

 transmitted hght ; arti- 

 hcial hght and a bull's- 

 eye condenser some- 

 times prove useful. 



The pressure out- 

 wards of the growing 

 tadpole gradually opens 

 out the leaf, so that 

 observation tends daily 

 to become more easy, 

 and the development of 

 head, gills, and tail can 

 be clearly seen. The 

 speed of development 

 depends largely on the 

 temperature of the 

 water ; but under 

 favourable conditions 

 the tadpole bursts from 

 his prison in about a 

 week. Before he does 

 this he is coiled up 

 like a watch-spring, and 

 may be seen at times 

 to give a jerky move- 

 ment in the egg. It is 

 one of such movements 

 that bursts the shell, 

 whereupon he floats 

 out into the water and 

 sinks. At this stage he 

 is to all intents and 

 purposes a fish. He 

 respires water by means 

 of gills, he shows no 

 sign of legs, and his tail 

 is slightly finned above 

 and below. Viewed 

 sideways against the 

 hght, he appears to 

 consist chiefly of two 

 black parallel lines, the 

 upper of which marks 

 the ultimate position of 

 his vertebral column, 

 and the lower that of 

 his digestive tract. 

 Three blackish inden- 

 tations at the head end 

 of him show where his 

 mouth and eyes wiU be. 

 The whole of him is 

 cased in a transparent 

 filament. 



