176 ORGANIC EVOLUTION CONSIDERED 



This is the structure of the ears of invertebrates 

 when they have organs of hearing, but most inverte- 

 brates are destitute of ears. 



As to the location of ears, it is said that " In the 

 Clam, it is found at the base of the foot; some grass- 

 hoppers have it in the fore-legs, and others in the sides 

 of the abdomen, and in many insects it is in the wing. 

 Lobsters and Crabs have the auditory-sacs at the base 

 of the antennae." * The ears of vertebrates vary 

 much in the complexity of their structure, and are 

 located in the sides of the head. 



The above various positions of ears show that they 

 must have been independently produced. Even 

 among insects they are found in at least three differ- 

 ent positions, namely, in the wings and legs and side 

 of the abdomen. 



Are the ears of invertebrates to be regarded as 

 homologous or as simply analogous? Whether one.or 

 both, it matters little as to the difficulty involved in 

 their evolution. It is claimed that organs at different 

 stages of their evolution may serve different pur- 

 poses. If this is true in the case of the ear, what 

 purpose could the ear serve during the first generation 

 of its growth? What would be the structure of this 

 organ at that time or at the end of the thousandth 

 generation? How could a rudimentary ear be pre- 

 served until it could perform the function of hear- 

 ing? 



We know of no answer to these questions. As 

 already stated, Darwin admits that "in many cases it 

 is most difficult even to conjecture by what transitions 

 many organs have arrived at their present state." 



The breathing apparatus of animals presents other 

 difficulties. All animals must absorb free oxygen. 

 Those that obtain oxygen from solution in water are 



* Orton's Zoology, p. 178. 



