68 DEVELOPMENT OF THE TADPOLE. 



resting the animal for a short time on absorbent tissue, such as 

 blotting-paper or linen, till the epidermis was nearly dry, and then 

 quickly weighing first in air and then in water, the specific gravity 

 being obtained in the usual way by dividing the loss of weight in 

 water by the weight in air. As of course it was quite impossible 

 to attach the embryo or animal to a hair or other non-absorbent 

 material without injuring it, a specific-gravity bottle, with wide 

 mouth and grooved stopper, was utilised for the purpose. The 

 animal could be thus twice weighed with a minimum of discom- 

 sort, no permanent injury having apparently been inflicted on a 

 single specimen during the process. A little difficulty, indeed, 

 was at times experienced during the weighing in air from the 

 lively nature of some of the specimens after their legs had 

 appeared and before the tail was entirely absorbed. These lively 

 individuals, by applying their moist though not wet bodies to the 

 sides of the dish, would rapidly crawl, or rather glide, to its edge, 

 and there remain perched generally a sufficiently long time for the 

 weighing to be accurately performed. 



(letting a little older, and perhaps bolder, some of them would 

 with a bound spring from the bottom of the receptacle to the 

 edge, and from thence take a long leap into the outer world. Not 

 a very extensive world either, as far as they were concerned, for 

 the majority of these tiny creatures failed to jump farther than the 

 bounds of the balance case, whence they were soon restored to 

 their own element. One huge fellow, however, who had grown 

 and fattened on the best of the land, or rather water, after 

 having experienced this kind of treatment two or three times 

 on various days ; in his attempts to baffle any further experiment 

 on himself, took such a desperate leap just as the weighing was 

 finished as to alight on the floor, having fallen through the 

 enormous height of about four feet, or approximately from 

 seventy to eighty times his own height. There he lay, poor 

 wretch, apparently dead, but in reality only stunned, for on care- 

 fully picking him up in order not to lose the carcase altogether he 

 showed such renewed signs of animation as to lead me at once to 

 replace him in his tank, where he lived and grew many days after. 

 But more of this individual at a later stage of our history. The 

 results obtained by this process of taking specific gravities were 

 most interesting. 



