70 



BOYS AND GIRLS IN BIOLOGY. 



First, on the outside, you see a clear, glassy-looking 



rim ; inside of this is a thicker, darker ring, filled with 

 granules, or little grains (Fig. 67). The centre of 

 the cell is quite clear, and contains a vacuole, or thin 

 space, like that which you saw in the torula. The 

 outer border is called the ectosarc, which means outer 

 flesh ; the inner is the endosarc, or inner flesh (Fig. 

 67). In the clear outer flesh, or ectosarc, you will 

 find the kernel, or nucleus, a roundish, solid-looking 

 little body, which does not change its form. If you 

 look attentively, you will see a little, round, clear space 



in the outer flesh, or ectosarc (Fig. 67), which has a 

 movement something like the beating of the heart. In- 

 deed, by some it is thought to be the simplest form or 

 beginning of a heart. It is called by a long name — the 

 " contractile vesicle, or space ; " but all amceb^ do 

 not have a heart, nor do they all have a kernel, or 

 nucleus. This " contractile space," or heart, is very 



Fig. 67. 



