ANGtJIS FRAGILIS. 87 



side, often falling and beginning again until on the merest tip of 

 their tail' they rested. Not " tip-toe " they stood, but as nearly 

 like it as possible. Even then a good deal of time and patience 

 were requisite before they could stretch themselves sufficiently to I 

 get their head upon the edge (because they might sink on the . 

 sand and moss), but this accomplished they would draw them- 

 selves up and over, and so down on the other side. Space forbids 

 any lengthened history of my many tame slow-worms, but as pets 

 they are most cordially recommended. Clean, quiet, gentle, 

 harmless, and easily managed, they will be found most interesting 

 and — yes, I may truthfully say, intelligent too, as they evidently 

 profited by experience in climbing and in mastering the covering 

 of net made sure by an elastic band. That they are not " blind " 

 their pretty bright eyes declare. The reputation of blindness 

 probably arose from their being found with closed eyes when hiber- 

 nating in company with snakes, whose open eyes would present 

 a contrast. Nor are they " deaf," as I took great pains to ascertain 

 by various experiments, until " Lizzie " (the slow-worm who was 

 longest under tuition) learned to recognise certain sounds made 

 to attract her attention, and the peculiar intonation of voice used 

 to her only ; and these from across the room were persisted in 

 until she looked round. Other experiments, and much more 

 about the slow-worms have been recorded elsewhere, and perhaps 

 read by some of our young collectors ; and the limits of this 

 little book demand that one must hasten on to the great herpeto- 

 logical event of the year 1886, viz., the discovery of the third eye 

 in lizards. 



Through this the poor despised " slow-worm," " blind worm," 

 " deaf adder," with all its misnomers, has become a very distin- 

 guished little reptile ; for in it was the discovery first made. We 

 must not here attempt more than a glance at this remarkable 

 organ which is now found to exist in various stages of develop- 

 ment in many vertebrate animals. It affords another illustration 

 of the principle of progressive development described in Chapter 

 VII. Eyes, like other organs, had their beginnings. As we saw an 

 incipient backbone in the Tunicate tadpole, and an " eye-spot of 

 complicated, lens-like structure," a half-ossified sternum and skull 

 in some of the Batrachians, and so forth, so there are incipient 

 eyes, single eyes, improved eyes, and perfect eyes in the various 

 sub-kingdoms. Some enable the animal merely to distinguish 

 light from darkness, yet these are an advance on no eyes at all, 

 as in the lowest forms. 



This " median eye," so called from its central position, is also 

 called a " parietal eye," being connected with the parietal bone 



