104 -^^^ Insides and the Worhjngs of Living Things 



cepted by most people without arousing any wonder. 

 After all, what use can cave animals make of functional 

 eyes? The interesting thing about this blindness is the fact 

 that cave animals have reduced sightless eyes, although we 

 might suppose that animals specially created for the dark- 

 ness could logically be produced without eyes in the first 

 place. Moreover, some of the blind crustaceans found in dark 

 caves have the eye stalk like that in a crab; but the see- 

 ing part of the structure is absent. The presence of the 

 eye stalk would need to be explained if we assume that the 

 species was specially created for its particular abode and its 

 particular mode of life. The presence of rudimentary struc- 

 tures is, however, quite in harmony with the assumption 

 that these blind animals are descendants of animals that could 

 see. Incidentally, it is interesting to note that although the 

 blind cave animals in America are just as blind as those of 

 Europe, they are different kinds of fish and crustaceans in 

 the two continents. Cave animals aside from being blind 

 are very much like the other animals of the corresponding 

 region — not like cave animals in other parts of the world. 



Analogies 



In the fall every gust of wind carries multitudes of 

 seeds from many diflFerent kinds of plants. Some of these 

 seeds have flat expansions or leaflike attachments which 

 are commonly spoken of as " wings." Not even a little 

 child is deceived by this word into thinking that the seeds of 

 the maple, for example, propel themselves through the air 

 as do birds, by means of their " wings." These expanded 

 structures are wing-like but they are not wings, and we say 

 "wings " as a short cut, to avoid awkward speech like " thin 

 spread-out portions that suggest the wings of birds." The 

 resemblance between two different structures in such cases 

 is sufficient to warrant the use of the same name, notwith- 

 standing the many important differences between the 

 objects. 



