CHAPTER XI 



THE ARCHITECTURE OF THE GERMPLASM 



1. DROSOPHILA, THE BIOLOGICAL CINDERELLA 



JUST as the bacteriologist firmly believes that guinea- 

 pigs were specially created for serological experimenta- 

 tion, so the geneticist has come to realize that the 

 banana-fly, Drosophila melanogaster, to which repeated 

 reference has already been made, was designed for 

 disclosing the secrets of the "architecture of the germ- 

 plasm" (Weismann). 



This tiny ubiquitous fly (Fig. 32), which hovers 

 around bruised fruit without regard to place, is so 

 small and harmless that it does not even qualify as 

 a pest. It has proved, nevertheless, to be a veritable 

 bonanza to the geneticist. It has many well-defined 

 characters that can be observed under the microscope 

 and it lives successfully upon a bit of banana in a milk 

 bottle plugged with cotton. Every ten or eleven days 

 a pair produces two to three hundred descendants that 

 in turn are ready to produce similar families of their 

 own so that the investigator who begins with them needs 

 to be an expert bookkeeper in order to be able to record 

 his results. Although, like Cinderella, Drosophila 

 comes from the humble environment of the garbage can, 

 yet this fly has easily outstripped all its sister competi- 



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