698 



SCIENCE. 



[N. S. Vol. XX. No. 517. 



doms.' To admit a plant cytology and an 

 animal cytology is only less absurd than 

 to admit a mammalian cytology, an avian 

 cytology and a reptilian cytologJ^ 



What is true of cytology is true of the 

 other branches of morphology such as em- 

 bryology in its broadest sense, the phe- 

 nomena of regeneration and regulation in 

 organisms, and especially the evolutionary 

 history of specific forms. While in tax- 

 onomy we must continue to have botanists 

 and zoologists, as we shall continue to have 

 ornithologists, entomologists, etc., yet out- 

 side of the purely descriptive subsciences 

 I would the gulf between botanists and 

 zoologists were annihilated and that we 

 had biologists separated rather in regard 

 to subjects and university chairs, journals 

 and societies devoted to evolution, cytology, 

 ontogenetic processes and form regulation 

 Avithout regard to the systematic position 

 of the material studied. Then we might 

 hope to advance a subject instead of mull- 

 ing over endless descriptive details. 



We have next to consider the relations 

 of morphology to form evolution or phy- 

 logeny. Before we can consider how a 

 new form arises we must clear the field by 

 seeking some element of form. The mass 

 of material in the organic, like that in the 

 inorganic, world early led to an attempt 

 at the classification of these materials in 

 both biology and chemistry. In chemistry 

 a certain number of ' kinds of materials 

 have in course of time been catalogued 

 and are called substances, each of which 

 has its particular molecular composition. 

 In biology likewise many thousand kinds 

 of organisms have been catalogued, and 

 these are called species, each made up of 

 particular sorts of individuals. Chemistry 

 has gone a step further in its analysis of 

 inorganic matter and recognized that the 

 different molecules are made up of diverse 

 combinations of a relatively small number 

 of units called atoms. To-day biology has 



to recognize that its individuals are like- 

 wise diverse combinations of units— rela- 

 tively very numerous — which, following de 

 Vries, we call unit characters, or we may 

 use the simpler name of 'characteristics.' 

 Characteristics are thus to individuals what 

 atoms are to molecules. As the qualities 

 and behavior of molecules are determined 

 by their constituent atoms, so the essence 

 of the individuals of any species is de- 

 termined by its constituent characteristics. 

 And as we may construct new substances 

 at will by making new combinations of 

 atoms, so we may produce new species at 

 will by making new combinations of char- 

 acteristics. The making of new combina- 

 tions in molecules or species is a useful 

 work, but it is not evolution. Evolution in 

 the inorganic or the organic world is first 

 achieved when we can make new atoms or 

 new characteristics, as the case may be. 



This conception of species, which has 

 arisen during the present decade, has its 

 germ in the work of Mendel, and in con- 

 sequence of the stimulating researches of 

 de Vries, Correns, Tschermak, Bateson and 

 others has developed into a stately doctrine, 

 a doctrine which bids fair to revolutionize 

 biology as the atomic theory did chemistry. 

 It adds at once a new dignity and interest 

 to morphology as well as to the description 

 of species or taxonomy. In desci'ibing the 

 form of an animal we are enumerating its 

 qualities. Many of these are directly the 

 unit characters of the species; others are 

 composite and may be analyzed, by appro- 

 priate methods of breeding, into the ele- 

 mental characteristics. 



I may illustrate this by reference to 

 domesticated poultry, to Avhich I am now 

 paying some attention. It is impossible 

 to enumerate all of the characteristics of 

 poultry, but the following are some of the 

 most striking: 



Size: Large and dwarf, which are ex- 



