X. 



THE E VIDENCE FROM DE VE LOP MENT (continued). 



II. THE LIFE-HISTORIES OF STAR-FISHES AND CRUSTACEANS. 



ALLUSION has already been made in the preceding chapter to that 

 most fundamental proposition of modern biology which maintains 

 that " community in development reveals community of descent." 

 It has also been shown at length that, in the eyes of modern natural- 

 ists, the development of an animal or plant is regarded as affording 

 a clue to the manner of its evolution .or descent from pre-existing 

 forms. The formation of a living being to-day, in other words, 

 repeats for us the formation of its race and species in time past. So 

 that, once again to quote Darwin's words, " we can understand how 

 it is that, in the eyes of most naturalists, the structure of the embryo 

 is even more important for classification than that of the adult." 

 Or, again, " embryology (or development) rises greatly in interest 

 when we look at the embryo as a picture, more or less obscured, of 

 the progenitor, either in its adult or larval state, of all the members 

 of the same great class." 



Second to none in interest, in the eyes of modem biologists, 

 are the phenomena presented to them in the formation of the 

 animal or the plant frame. In former years the mystery of 

 development was great indeed. There could be offered in the 

 past decade of biology no reason appealing sufficiently to the 

 rational intellect as explanatory of the events in question why a 

 frog in its development should appear first as a gill-breathing fish, 

 later on as a tailed newt-like creature, and ultimately as a tailless 

 lung-breathing amphibian. Nor could natural historians in the past 

 venture to account in more lucid fashion for the curious changes 

 which a butterfly or beetle undergoes in its progress from the days of 

 its youth towards the adult form, and from the stage of the crawling 

 grub, through that of the quiescent chrysalis, to the full-fledged 

 " imago " with its wings. Kirby and Spence summed up and dis- 

 missed such matters in a manner unfortunately for the free play of 

 intellectual vigour, not quite extinct in these latter days which said 

 much, perhaps, for faith, but little or nothing for reason and 

 science. These famous entomologists held that insects passed 

 through a metamorphosis because "such is the will of the Creator;" 

 and they supplement this " confession of faith " with an attempt at a 



