S..I.I.AS On the Or it/ in f I '> /'/<. 11.") 



numerous In make this result of a free larval existence clearly appear, so that th" 

 not vnrv InLrhlv endowed aiiiiunl m:iv enjuv tin- :nlult state for a very considerable 

 period. To rightly estimate the value of this hypothesis, we ought to know at 

 lca>t :i|>pn'xiiii;itclv tin- limits of age of various animals in the adult state-, and the 

 length "f time they respectively pass in the larval state, as well as the changes 

 which they pass through ; and these data are almost wholly wanting, and not 

 uimatimillv, since no intelligent man, unprompted by some suggestions such as 

 here made, would care to set about the laborious investigation which their 

 ascertainment would involve, merely for the sake of tabular results. Something, 

 however, may be learnt from various of the higher animals. Thus we may point 

 to the Kphemeridae, which, after a prolonged larval existence, die soon after 

 attaining maturity. So, too, the butterflies and moths, which do not live long 

 after ovi position. A still more important consequence, however, would seem to 

 follow from the premature ageing due to a free larval existence ; and that is the 

 comparatively early exhaustion of the power of undergoing transformational 

 change; tin- adult or comparatively stable state is reached sooner than it other- 

 wise would be, and the chances of further development are correspondingly di- 

 minished. 



If we pass to the consideration of the opposite case, wo find that the embryo 

 within the egg is in a much superior position to the free larra. In most cases, all 

 that it has to do, besides undergoing transformational changes, is to feed upon 

 nourishment already prepared for it, needing scarcely any preliminary digestion, 

 but capable of immediate absorption by the cells of the embryo. When the 

 embryo is hatched, it enters upon the world with its cells scarcely used ; their 

 capacity for work has comparatively had small demands made upon it, and thus a 

 longer life awaits them in the mature state, when the faculties of the organism 

 are most highly endowed. 



Thus, in contrast with the Ephemeridae, we may cite the ants and bees, which, 

 while in the larval stage, are carefully nourished at the expense of the com- 

 munity, and some of which, after leading the life of grubs, enjoy an interesting and 

 protracted existence. Further, the cells of a young animal just born would 

 appear to be in a particularly plastic state, so that they are peculiarly ready 

 to respond to the action of the environment. Many changes might be induced in 

 the young animal at this critical period, the effects of which would be afterwards 

 manifested as variations in its offspring. 



Again, the longer life in the mature state, acquired by those forms which are 

 saved from the drudgery of a larval existence, offers increased opportunities for 

 evolution to the adult animals, so that a progressive development starting from 

 higher and higher platforms is directly favoured. 



But not only is a longer existence assured to the adult existence in the 

 embryonic state is shortened, and perhaps here the influence of seclusion is most 



