1044 Recent Literature. [Oct 
which natural selection is completely excluded, and the nature of 
the species itself definitely determines the direction of the — 
changes, nevertheless show variability from the ve inning, — 
we may venture to conclude that every transformation of a 
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a fixed direction which entirely depends on the physi l 
of the varying organism, and ‘is different in different species ot 
even in the two sexes of the same species.” j 
Weismann insists that too little is ascribed to the part 
become transformed into a mammal, or to express 
ally, why, from a given: starting point, the develo 
ticular species cannot now attain, even under the most 
external conditions, any desired goal; and why, 
ing-point, given courses of development, even when ot Co 
able latitude, must be restricted, just as a ball roine 
hill is diverted by a fixed obstacle in a direction determi 
the position of the latter, and depending on the direction 
tion and the velocity at the moment of being diverted. 
he remarks: “If, under heredity, we comprise ts e. 
1 See my essay, Ueber den Einfluss der Isolirung auf die Artbildung: 
1872.” i 
