THE LAW OF BIOGENESIS 7 1 



that has several tissues In Its body, he observes a 

 marked distinction between the cells that are de- 

 voted to carrying on the dally activities of living 

 and those that become active rhythmically, such 

 as the cells that produce the blossoming flowers 

 in spring. 



The cells that keep the body alive and are busy 

 In digesting, breathing and responding to the mani- 

 fold stimuli of their immediate environment, 

 grouped into muscle, nervous, skeletal and various 

 other tissues, or leaves, branches and roots, are 

 termed the somatic or body tissues. This variety 

 of activity results in producing cells that become 

 highly specialized. Of course such cells constitute 

 the bulk of the body of plants, animals and man. 

 They are by far the most highly differentiated 

 tissues and their cells participate In vital processes 

 that are extremely difficult of description. 



In marked contrast with these highly specialized 

 cells, that one can readily recognize at a glance 

 under the microscope, are the relatively simple 

 cells, termed the germ or reproductive cells. The 

 germ cells never unite to form tissues and never 

 participate In such general bodily activities as 

 movement, food-getting, excretion, etc. Their 

 activity is periodic even in aquatic animals In 

 tropical waters, where they are recorded as pro- 

 ducing young at regular intervals. 



During the remainder of the time, these germ 



