38 



DEGENERA TION. 



small, it is true, whilst the palps and daggers of the 

 spider have dwindled to a beak projecting from the 

 front of the globular unjointed body. In the other 

 the eight legs have become mere stumps, and the 

 body is elongated like that of a worm. 



w. 



Fig. II. 



Fig. 



Fig. II. — Acarus equi. A degenerate Spider or mite parasitic on the skin of the 



hf rse. 

 Fig. 12. — Degenerate Spider (Demodex foliculorum) found in the skin of the human 



face. 



The instances of deepen eration which we have so 

 far examined are due to parasitism, except in the 

 example of the Barnacle, where we have an in- 

 stance of degeneration due to sessile and immobile 



