COMPLEXITY OF STEUCTURE. 1 49 



lings in a nest no bigger than a cricket-ball, or the still 

 tinier Etruscan shrew, it greatly enhances our interest to 

 know that every essential organ is there which is in the 

 giant rorqual of a hundred feet. The humming-bird is 

 constructed exactly on the same model as to essentials as 

 the condor ; the little sphaerodactyle, which we might put 

 into a quilbbarrel, and carry home in the waistcoat pocket, 

 as the mighty crocodile ; the mackerel-midge, which never 

 surpasses an inch and a quarter in length, as the huge 

 basking-shark of six- and- thirty feet. 



Complexity of structure, the multiplicity and variety of 

 organs, do not depend upon actual dimensions, but rather 

 upon the position in the great plan of organic existence 

 which the creature in question occupies. The harvest 

 mouse possesses a much more elaborate organisation than 

 the vast shark or, colossal snake. In general, the creatures 

 of simple structure are minute, — the most simple, the most 

 minute ; but we need to limit this proposition by many 

 conditions and exceptions, before we shall fully apprehend 

 the true state of the case. Ignorant exhibitors of oxy- 

 hydrogen microscopes will frequently, indeed, be heard to 

 declare that all the specks that are seen shooting to and 

 fro, or revolving, top- fashion, in their populous drops of 

 water, are furnished with all the organs, tissues, and 

 members, that constitute the human frame ; and similar 

 statements were not unconimon in cheap compilations of 

 natural history a few years ago. This has been abund- 

 antly shewn to be erroneous; but the tendency has been to 

 run into an opposite extreme ; and to assume ijfat what are 



