$8 THE MYSTERY OF LIFE. 



early period all these bioplasts were spherical, 

 all had been formed by division and sub-division 

 from the same original bioplasm mass. The 

 nerve bioplasm cannot by any means known be 

 distinguished from the bioplasm to take part in 

 the formation of muscle, or either of them from 

 connective tissue bioplasm. Nor was there at 

 this early period, when the basis tissue of the 

 heart was being formed, a vestige of muscular or 

 nervous tissue. There was the living matter, 

 by which alone the formation of such tissues 

 is possible, but that was all. As development 

 advances, however, the little bioplasts move 

 away from one another, and in their wake, or 

 in the interval between them, tissue makes its 

 appearance. In this process the matter of the 

 bioplast is changed, it loses its powers of growth 

 and multiplication, and acquires the form and 

 properties of tissue. But only part of the 

 living matter undergoes this change. The bio- 

 plast does not disappear ; it continues to take 

 up nourishment and convert this into bioplasm, 

 and at this early period of life, faster even than 

 its substance undergoes conversion into tissue. 

 Thus the loss of bioplasm by transformation 

 into tissue is more than compensated by the 



