FIRST INDICATIONS OF LIFE. 231 



the two sides correspond to one another. A symmetry is 

 thus established, but there is as yet no head, there are no 

 limbs, there is no tail, neither can we recognize the sides of 

 the body-wall, though we see that there is something coming. 

 All this is brought about without any help from organs such 

 as we recognize in the adult animal. There is as yet not 

 even a drop of blood, nothing but a modified yolk, no longer 

 yellowish, but rather milky in appearance, and somewhat more 

 translucent than yolk. Presently, something quite startling 

 in character begins outside. Dots make their appearance, 

 and these dots move. They change places, they cross each 

 other, they rise and fall, jumping and hopping about often 

 with a jerky motion. In all this movement, even under a 

 high power of the microscope, no fixed tendency, no given 

 direction is perceptible. They are only rising and felling, 

 heaving and subsiding. These dots are still yolk. They are 

 perhaps of a little deeper yellow then yolk ; you might 

 almost imagine them to be particles of blood ; but on careful 

 examination you see no vessel and no indication of a regular 

 current flowing to and fro. Presently, in the midst of these 

 leaps, this heaving and falling, one dot may be seen to turn 

 around another, and this may be repeated at difierent spots ; 

 two dots not very far apart may exchange places, the one 

 which is here may presently be seen there, the one which 

 was there may presently be seen here, and after a while 

 the whole yolk seems to be disintegrating, breaking up. In- 

 stead of holding together, it looks as if it were crumbling to 

 pieces. After awhile the moving particles on one side 

 march in one direction, and those on the other march in the 

 opposite direction, passing on until they are brought under 

 the gei-minative layer. This is, in fact, the first sign of cir- 

 culation. But there are «till no vessels, no channels. They 

 run as dirt will run after a rain over the surface, or as gravel 

 may be carried by a heavy shower into open channels. Thus 

 running, they perhaps form a puddle in one place ; this pool 

 increases in dimensions, and presently a stream shoots out 

 from it in one direction, and this stream unites a little further 

 out with another, formed in the same way. Now you have 

 circulation, but it is not yet blood, nor are these channels 

 closed. They are simple furrows in the substance of the 



