214 THE QUANTITATIVE METHOD IN BIOLOGY 



are comparatively simple, and we enjoy the inestimable advant- 

 age of having at our disposal not only recent species but numer- 

 ous series and innumerable specimens of fossil species from all 

 the geological periods. By means of tables of constants the 

 facts may be set in order. Here we must, of course, begin with 

 the investigation of the recent forms, in order to pave the way 

 for the study of their fossil analogues.^ 



The history of the progress of physics and chemistry teaches 

 us an important lesson : here the quantitative method has been 

 applied more and more to the study of minutiae. The con- 

 structors of instruments have been asked continually for 

 more perfection in their balances, thermometers, goniometers, 

 galvanometers, thermostats and other implements, in order to 

 penetrate deeper into the quantitative knowledge of small things 

 which were previously neglected. Along this road marvellous 

 discoveries have been made. In a similar way much progress 

 may be achieved in biology by the measurement of minutiae 

 which are primordia. By the work of the Mendelian School 

 and by the application of the quantitative method to system- 

 atics, the road is opened. 



§ 149.— THE NOTION OF SPECIES.— This notion is in 

 reality the comer-stone of biological science. In Part I. I have 

 expounded a hypothesis according to which the notion of species 

 is a chemical notion, and each species is strictly different from aU 

 others. Adopting the latter principle, I deviate from the Dar- 

 winian doctrine of the continuity of the forms of life which is 

 still accepted by the great majority of the biologists. I am, 

 however, not alone. 



It may be remarked, at first, that DARWIN himself, 

 especially in some of his later works, has repeatedly pointed 

 to the occurrence of sudden variations or sports, by which a 

 specific form might possibly be transformed into a new one 

 (saltation). 



"... GALTON (1889) is of the opinion that the aberrant 

 or discontinuous variations generally known as sports may be 

 of considerable significance in evolution. Because evolution 

 may proceed by minute steps, he considers that it does not by 

 any means follow that it must so proceed. 



" Again, within recent years the orthodox view (continuity) 

 has been ably combated by BATESON in his book on variation 



^ For instance, the study of the fossil Brachyopods, Pectens, Cardiums or 

 Echinids should be preceded by the quantitative investigation of the primordia 

 of the recent species of the same groups, because it is possible to obtain about 

 the latter information in respect of individual development (embryological 

 series, see p. 194 ; embryological curves, see p. 61 and 158), conditions of exist- 

 ence (plasticity) and even hybridization. Beginning with the fossils, we would, 

 I am afraid, put once more the cart before the horse. 



