AMBLYSTOMA PUNCTATUM. 17 



boflily. This larg;e supply of foocl-material enablcfl tlicse larger 

 inflividuals to increase still more rapidly so that in two weeks 

 from the time they commenced feeding upon their comrades they 

 were ten times the size of one of the smaller ones of the same age, 

 yet undevoured. Thus there was an interesting case of natural 

 selection by survival of the fittest, going on amongst these young 

 forms. Those who by their activity and strength preserved their 

 branchife uninjured, develop so much faster than their brethren, 

 as to enable them to pass through all their changes in the water 

 and leave that element to seek for regions where food was more 

 abundant. The power of reproduction of lost parts by this class 

 of animals is so well-known that it seems remarkable that these 

 young forms should not have reproduced their lost and mutilated 

 branchire. But, on the contrary, not a single specimen of the many 

 hundreds who suffered such losses, succeeded in restoring the lost 

 parts. This may have been due to the small amount of food with 

 which they were at that time supplied. 



The branchial clefts have not been mentioned for the reason that 

 they do not appear until after the branchise have become so large 

 as to cover up the places where the clefts and arches make their 

 appearance. It thus being impracticable to satisfactorily decide 

 this point from external observations, it is left for the present and 

 will be solved when I work up the changes in internal structure. 

 For this work upon the internal parts I have preserved a large 

 series of specimens in the various stages of development from 

 which it is hoped, by means of sections, to get quite a complete 

 history of the changes which there take place. 



EXPLANATION OF THE PLATES. 



The outlines of all the figures were obtained with the aid of the 

 camera lucida. 



PLATE 1. 



Figures 1 to .5 are enlarged 18 diameters. 

 Figure 6 is enlarged 21 diameters. 



Figure 1. — The lower side of an egg which has just completed seg- 

 mentation; v. p. the area of large, light colored ceils 

 that are to form the vitelline plug; v. p. f. the begin- 

 5 



