126 Notes on the Natural History of the Natterjack. 



observation; but the next following changes went on rapidly, 

 and voluntary motion had begun at the end of twelve days from 

 the exclusion. The eye was well formed at an early stage ; but, 

 although the spawn was first seen near the end of March, the 

 middle of July had passed when the legs made their appear- 

 ance ; and this they did with some difference, for in some 

 instances the feet of the hindmost legs were first protruded, 

 and in others those of the first pair were first seen. At this 

 time some were in possession of four limbs, with scarcely the 

 vestige of a tail ; and this is the period when the colour changes 

 from black to bronze, which last-mentioned appearance is a 

 sign that the creature is about to leave the water for the land. 

 As the tail becomes less the body diminishes in size, so that, 

 when the tail has disappeared, the body has become less than 

 half as large as when in the tadpole state ; the greatest breadth 

 being a little behind the eyes. At this time, that is, a few days 

 after the middle of July, being desirous of knowing what effect the 

 presence of sea-water would have on these little creatures, I 

 removed from their native pool three specimens which had 

 obtained their fore-legs, but still possessed a small remnant of 

 tail, together with one which was furnished with only two 

 legs and a tail at its full length. To the water in which they 

 were placed there was added a fourth part of sea-water, with 

 which mixture in a few minutes they were greatly affected, 

 and after a quarter of an hour those with the legs appeared to 

 be dead. One of them lay with its mouth wide open, and the 

 legs of the others were stiffly stretched out, and they were 

 thrust about unconsciously, sometimes on their backs with the 

 motion of the water ; while that one which still retained its tail 

 appeared to be little affected, so that in its movements it thrust 

 about its companions at pleasure. They remained in this con- 

 dition for half an hour, after which this water was removed, 

 and fresh water from a brook supplied to them ; in which for 

 another half hour the apparently dead tadpoles remained in 

 the same condition ; but, having set the vessel aside for two or 

 three hours, when next examined they all were as lively as at 

 first. It appears, therefore, that a mixture of sea-water is 

 fatal to them at a later stage of growth, but that at first it 

 does them little or no harm. 



( m the following morning the tadpole with the tail had 

 acquired its fore-leg on the left sido, and by the evening its 

 companion leg bad appeared \ both of them perfect in form, but 

 bent on themselves, and enclosed in a membranous sheath. 

 The growth of these legs in stoutness is rapid, and presently 

 after their appearance the body behind the aperture of the 

 gills contracts in its dimensions. The margin of the fin on tho 

 border of the tail becomes waved before the hindmost legs 



