( 453 ) 



everywhere without geographical separation. For, if a greater number of individuals 

 proceed in a certain direction of development, while others remain behind, a new 

 species must necessarily spring up. This progression of a greater number of 

 individuals can take place in the middle of the area of a species, if these individuals 

 are more sensitive against the e.Kterniil conditions than the remainder of the 

 species." — Is the greater individual sensitiveness hereditary in all the offspring of 

 the more sensitive specimens ? This is what we have to prove : we must not merely 

 assume it. For, if the new and old form, resp. the offspring of the " sensitive " 

 specimens and the less sensitive ones, mix, the parent stock will not remain stagnant, 

 as " Epistasis " imjdies ; it will follow the more sensitive individuals. And as there 

 will be differences in the degree of sensitiveness in the jiarent stock as well as in 

 the assumed new form, it is not intelligible bow a gaji that would separate the one 

 original species into two can come about. 



Orthogenesis may be a process in Evolution, but it is certainly not a cause 

 The question is, which of the many possible general lines of development will be 

 followed by the geograjihically separated members of a species, and there is nothing 

 in the above arguments which shows that the eventual course to be followed by a 

 species in a certain area does not depend on the biological conditions of this locality. 

 An individual has many characters, a race many individuals, cajjable of varnno- in 

 different directions. A general force, gravitation, brings the particles of the water 



of a river onwards; the direction of the movement of every molecule is as every 



"direction"— geometrically straight at every place, at every moment, but the 

 meandering course of the river depends not on that general force, but on the 

 external conditions the water has to cope with. 



At the bottom of the conclusion that species originate in the way as maintained 

 in Arthildung is the opinion to which expression is given in I. p. 10 : " It is a main 

 object of my researches to prove, that the same factors which are the cause of the 

 aberrational characters of individuals, and produce the ' Abarten,' must also "-ive rise to 

 species; this folic iws irrefutably already from the fact that the distinguishing charar- 

 ters of species are the same as those of ' Abarteu,' and the characters of the latter 

 the same as those of individuals." — The reader who is not more closely acquainted 

 with the insects upon which the researches in Arthildung are based, may easUy be 

 deceived by the arguments in favour of the above contention — a contention it is, not 

 a " fact." For he is liable to overlook (1) that in ArthHilimy aberrant individuals are 

 treated either as aberration or as " Abart," just as it is thonglit best in that jilace, (2) 

 that forms of dimorphic species are designated as " Abarten," (3) that different broods 

 of the same country are considered " Abarten " and " Abartungen," (4) that one and 

 the same individual aberration, or seasonal form, or dimorphic form are treated in 

 the descriptive part of Arthildung correctly as what they are, wjiile in the general 

 part, where the conclusions are drawn, they appear as " Abarten," or even " Arten." 

 Thus we learn in 11. p. 23, that the hVncV Je male of I', tunius is an "Abart" 

 {P. turnus glaucus), while on ji. 28 we find the same form designated as a species 

 (P. glaucus), and on p. 142 as P. turnus var. glaucus. The individuals of Papilio 

 podalirius with 11, 10, 9 bands are correctly said in I. j). 41 to be individual 

 aberrations, unfortunately named P. iwdidirius undiximlineatus,!'. p. decemlineatus, 

 P.p. novendiiwatas, while in Urt/iogenesis, p. 4S, that same aberration undecimlinmtus 

 is brought forward as an " Abart" of podalirius. Dark individuals of P. pkilolaua 

 are described as abc^rration and named P. pkilolniis nigrcxrcru; nielanistic specimens 

 are said in Orthogenesis, p. 40, to form an aberration of the aberration rdgresceus, and 



