SOMATOGENESIS 263 



surely the time element as it appears in the acceleration 

 or retardation of the processes concerned. Not all 

 tissues or organs develop at the same rate. Some out- 

 run others necessarily in order to prepare the way for 

 what follows. Under normal conditions in ontogene- 

 sis things swing into place in the nick of time to make 

 the next step possible. When these rhythms are upset, 

 just as when Field Marshal Grouchy at Waterloo 

 failed to swing his troops into line at the critical mo- 

 ment, then there results a Waterloo in the organism. 

 To any one who has followed in detail the intricate 

 stages of ontogenesis in some organism, conditioned as 

 it is by its indispensable and modifiable environmental 

 complex, the wonder grows that the successes are so 

 many and the disasters so few. 



10. CONCLUSION 



It is not enough for the geneticist to know the chro- 

 mosomal machinery at the beginning of his story and 

 the Mendelian moral at the end of it. Between these 

 two fields of investigation lies the no-man's land of 

 somatogenesis which forms an important part of the 

 hereditary tale. 



The processes of somatic differentiation are so amen- 

 able to experimental interference that no doubt future 

 investigators will continue to be attracted to the cul- 

 tivation of this promising field of genetics. 



