THE EVIDENCE FROM DEVELOPMENT. 245 



eggs as food. Thus, whilst the young of the spotted salamander, 

 a neighbouring species, number 40 or 50 at a birth, those of the 

 alpine species number but two. Yet the two species are equally 

 numerous a fact showing powerfully how one animal, despite 

 disparity of numbers, may equal in vitality an apparently more 

 prolific race. For the two young of the alpine salamander, when 

 born, are large and active, have passed completely through their 

 development, and possess strong acrid skin-secretions ; whilst those 

 of the spotted species are comparatively helpless when born, and 

 have not got rid of their gills. Hence the latter are subject to a 

 greater mortality, and the proportion of adults to young is therefore 

 relatively small. On no rational theory of nature could it be believed 

 that a young newt was provided with gills, and that, thus furnished, it 

 was destined to be developed within its parent 's body. The two facts 

 of the presence of gills and the development of the alpine sala- 

 mander within the parent body are in utter opposition to each other. 

 Further, we know that when taken from the parent body, long prior 

 to their natural period of birth, and placed in water, the young of the 

 black salamander live and breathe by their gills, as was undoubtedly the 

 original habit of the species. Placed in water, the young beings live 

 for weeks, and ultimately develop from their water life into land sala- 

 manders. But in this latter experiment, the full development of the 

 young occurs weeks after the time when they would have been 

 moving actively on the Alps, had they been left to their development 

 within the parent frame. Thus we see, firstly, that the modern 

 development of this animal is clearly acquired even the curious habit 

 of the two larvae eating the other eggs clearly proves as much. And 

 secondly, we again come face to face with a case of shortened and 

 condensed development, favouring at once an early maturity and the 

 increase of the race. Probably a rise of land, carrying these sala- 

 manders farther and farther from water, was the direct cause of the 

 altered mode of life of the alpine salamander. We know that this 

 new adaptation is of relatively ancient origin, for the gills of the 

 salamander, placed in water, shrink by a natural and vital process of 

 absorption, and not through mere drying and shrivelling as in the 

 axolotl. The acquired process of gill-absorption has become, in 

 other words, an inherited matter has become part and parcel of 

 the animal's constitution. As, therefore, their watery pools were left 

 below by the rise of land, the salamanders would gradually acquire 

 the habit of retaining the young within the body for more and more 

 lengthened periods; and in due time, the present state of matters 

 was evolved including limitation of numbers and acceleration of 

 development, along with the novel condition of utilising the remaining 

 eggs as a food-supply. 



An important and interesting feature in connection with the 



