132 



FOUNDATIONS OF BIOLOGY 



while the wings are new, unrelated structures and not modi- 

 fications of the primitive serial appendages of the ancestral 

 form. However, as we shall see later, the wing of a Bird and 



* en.3 



Q.Copul-jrory Organs lO.Swimming Foof 



ll.Urotx 



FIG. 72. Typical appendages of a Crayfish. All have been derived from a simple 

 biramoua appendage similar to the swimming foot (10). Protopodite, endopodite, and 

 exopodite are homologous throughout the series, en, 1-5, parts of endopodite; ep, 

 epipodite; ex, exopodite; fl, parts of antennule; g, gill; pr, 1-2, parts of protopodite. 

 (From Parker and Haswell, after Huxley.) 



the arm of Man are homologous, while the wing of an Insect 

 and the wing of a Bird are analogous structures. One of the 

 chief tasks of the branch of biology known as COMPARATIVE 

 ANATOMY is to discover the various parts of plants or of animals 



