SOME COMMON ERRORS CONSIDERED 105 



instance of defeneration, for its course is exhibited 

 even in the history of the individual. The larvae 

 of the barnacle are small free-stvimming Crustacea, 

 but as they develop (observe the distinction between 

 development and progress), they attach themselves 

 by the head to such suitable objects as a ship's 

 hull or a piece of floating wood. Thus the adult 

 or fully-developed barnacle is far inferior to the 

 larva, for it is little more than a fixed fleshy stalk, 

 upon which grows the body and its shell. Here 

 is a palpable case of what we call degeneration, 

 and, in accordance with the theory of recapitula- 

 tion, we find that the barnacle is descended from 

 species the individuals of which are free-swimming 

 both in youth and in adult life. 



Then, again, let us consider the case of the para- 

 sites. They amount to thousands on thousands, 

 both of animal and vegetable species. Their char- 

 acteristic is that they live upon or in the bodies of 

 individuals of some " higher " species. Now the 

 higher species are later in point of time. How did 

 the parasites gain a living before the evolution of 

 the higher forms upon which they now batten ? 

 Furthermore, it is evident that the primaeval forms 

 of life cannot have been parasitic, for no hosts were 

 forthcoming. Hence we are forced to the necessary 

 inference that all parasitic species are descended 

 from non- parasitic ancestors ; and this view is sup- 

 ported — not that it is in need of such support — by 

 the fact that many animal and vegetable species are 

 known, the individuals of which are independent in 

 their youth but parasitic when adult. In such in- 

 stances, both racial and individual, evolution and 



