122 THE CASE AGAINST EVOLUTION 



sharp line to be drawn between local varieties and species. In 

 Echinodermata, however, there is the additional difficulty that 

 the acquisition of ripe genital cells does not necessarily mark 

 the termination of growth; the animals can continue to grow 

 and at the same time slightly alter their characters. For this 

 reason many of the species described may be merely immature 

 forms. . . . 



"The disputes, however, as to the number of orders included 

 in the Asteroidea proceed from a different cause. The at- 

 tempt to construct detailed phylogenies involves the assump- 

 tion that one set of structures, which we take as the mark of 

 the class, has remained constant, whilst the others which are 

 regarded as adaptive, may have developed twice or thrice. 

 As the two sets of structures are about of equal importance 

 it will be seen to what an enormous extent the personal equa- 

 tion enters in the determination of these questions." {Op. cit., 

 vol. I, pp. 459, 460.) 



In dealing with fossil forms, these difficulties of the taxono- 

 mist are intensified: (1) by the sparse, badly-preserved, and 

 fragmentary character of fossil remains; (2) by the fact that 

 here breeding experiments are impossible, and hence the diag- 

 nosis based on external characters cannot be supplemented 

 by a diagnosis of the germinal factors. Fossil taxonomy is, in 

 consequence, extremely arbitrary and unreliable. Many fossil 

 forms classed as distinct species, or even as distinct genera, 

 may be nothing more than fluctuants, mutants, hybrids, or im- 

 mature stages of well-known species living today. Again, 

 many fossils mistaken for distinct species are but different 

 stages in the life-history of a single species, a mistake, which is 

 unavoidable, when specimens are few and the age of the speci- 

 mens unknown. The great confusion engendered in the classi- 

 fication of the hydrozoa by nineteenth-century ignorance of the 

 alternation of hydroid and medusoid generations is a standing 

 example of the danger of classifying forms without a complete 

 knowledge of the entire life-cycle. When due allowance is 

 made for mutation, hybridization, metagenesis, polymorphism, 



