1892.] 



THE BRITISH NATURALIST. 



137 



The first transformation of the egg is the breaking up of the yolk 

 into a cluster of little yolks. In this stage the insect resembles a ripe 

 blackberry. It is still so small as to be quite invisible to the naked 

 eye. What becomes of the white of the egg? What is called the 

 white of the egg is merely food. It undergoes no changes, but simply 

 nourishes the yolk, which is now like a cluster of small shot, or, as I 

 said, a blackberry. Not yet is there any visible essential distinction 

 between eggs of all kinds. The first transformation of the butterfly is 

 the blackberry stage ; so it is with the bird, and the rabbit, and the 

 fish. What is the good of if? 



Take to a jeweller a lump of turquoise stone, and tell him that you 

 want a ring set all round with turquoises. He could do nothing with 

 the lump, he must cut it into pieces in the proper way, and then he 

 could put the pieces round the ring, and a very pretty ring it would 

 be. What was the good of cutting the turquoise in pieces ; To apply 

 it to a practical use. Nature wants to do something with the jelly 

 cell, so the jelly is cleft in little pieces which are left sticking together 

 like the lobes of a blackberry, but quite ready to be arranged. This 

 is called the morula stage, and I think that when you remember that, 

 as a rule, this is a fact in the history of all animal life, you will admit 

 that it is interesting. ' , 



The next stage is rather harder to'describe. — We look again, the 

 blackberry shape is gone, but we see the little pieces all arranged in 

 beautiful order, covering the surface of a globe which is hollow, like 

 an india-rubber ball, and contains a jelly-like substance. If now I 

 take this india-rubber ball and squeeze it in on one side, I can form 

 a cup, or something deeper like a horse-shce, the sides of which are 

 double. This is the third stage, and, as a rule, it is common to all 

 animal life. The butterfly has passed through this form which is 

 called the gastrula stage. The hollow represents the primitive 

 stomach, and the opening the primitive mouth, and certainly all 

 animals need a stomach and a mouth. We have not yet arrived at a 

 stage which is plainly visible to the naked eye. The ordinary size of 

 a gastrule form is less than half a millimetre in diameter, the size of a 

 full-stop m ordinary print. Here, however, we have not only life but 

 the. simplest rudiment of animal form. The butterfly is actually 

 coming into shape, and, more than this, it is giving the first visible 

 signs that it is not going to come out as a monkey or a bird. 

 Distinctive characters now set in by degrees, something special shews 

 that the tiny embryo is not going to be an animal with bones, so the 

 vertebrates are left behind. A little further a mark crops out that the 

 embryo is not going to be a snail, so the snails are left behind; further 

 on the embryo takes a turn that is never taken by the egg of a star- 

 fish, so the star-fishes are left behind. Successively, points arise at 



