PRACTICAL CONSEQUENCES OF THEORY. 85 



the matter. As a practical man, he wants practical applica- 

 tions ; as for " theories," he doesn't care a silver fonrpence 

 for them. I will not turn round and humiliate him, by- 

 proving that of all blind theorists none are blinder than 

 the "practical men;" but v/ill rather captivate his con- 

 fidence, by showing him how the result he so earnestly 

 desires is only to be obtained after a remote excursion 

 into the obscure regions of science. He need not make 

 the excursion, but he must wait till it be made ; for it 

 is amusing to think that even so simple a matter as the 

 destruction of these vermin defied all ingenuity, until 

 Embryology came to our aid. I carefully abstain from 

 mentioning the unusual term in his presence, but address 

 a question to him : — 



" Are these animals of separate sexes ? " 

 He looks rather huffed, as he replies : " How should I 

 know ? and what does it matter V 



"It matters everj^thing. And for your satisfaction I can 

 tell you that they are of separate sexes." 

 "Humph !" 



" A French naturalist, Quatrefagcs by name, has found 

 that at certain seasons the female carries the eggs in the 

 folds of her respiratory organs." 

 " The deuce she does I " 



" And there they remahi till the milt of the male, float- 

 ing in the water, is washed over them, and fecundates 

 them. Now this same Naturalist has brought his know- 

 ledge to bear upon the very question you are so interested 

 in. He finds that a weak solution of mercury thrown into 



