November 2G, 1!)09] 



SCIENCE 



769 



rigorously orthodox Lamarckians or Darwin- 

 ians among biologists. Little by little, just as 

 modern houses are built with the ruins of 

 ancient temples, an ediiice has risen out of the 

 crumbling theories of Lamarck and Cope, of 

 Darwin and Wallace, of Eimer and Weismann 

 — an interpretation of evolution which retains 

 the tested facts of all previous attempts at a 

 general explanation and which, with no pre- 

 tense of finality, keeps the unbridged gaps well 

 in view. Seven years ago, I wrote for the 

 Revue an article' in which this theory was 

 anonymously set forth and I find it needs very 

 little modification at the present time. Ac- 

 cording to this theory, the unforeseen modifi- 

 cations of the germ plasm — whether called 

 mutations or sudden or discontinuous varia- 

 tions — produced at a last analysis by environ- 

 mental changes, are the source of the morpho- 

 logical and physiological differences that dis- 

 tinguish one definite species from another. 

 This, as will be readily seen, is neither La- 

 marckism nor Darwinism. Natural selection 

 controls development in animals and in plants 

 by the elimination of the individuals and spe- 

 cies not adapted to survive under given con- 

 ditions, a selection which permits only the 

 " fit " to exist. The adaptations indispensable 

 for life in given surroundings must therefore 

 precede chronologically these environmental 

 conditions and they are not determined by the 

 conditions to which they seem to correspond 

 with such nicety. Herein lies the most orig- 

 inal point of the theory and one that will, no 

 doubt, meet with the greatest opposition. I 

 prefer not to dwell upon it here but shall defer 

 its demonstration to a later time. 



THE FILLING OF UNOCCUPIED PLACES IN NATURE 

 AND THE ORIGIN OF ADAPTATIONS* 



In the theory of the survival of adaptive 

 mutations, as set forth above, neither La- 

 marckian factors nor the selection of minute 



' L. Cu^not, " L'6voIiition des theories trans- 

 formistes," Revue ginirale des Sciences, t. XII., 

 p. 264, 30 mars, 1901. 



'Cu^not, L., 1909, " Le Peuplement des Places 

 Vides dans la Nature et I'Origine des Adapta- 

 tions." Translated from Rev. gen. Set. pures et 

 appliq., Ann. 20, no. 1, 15 Janvier, 1909. 



variations determines the appearance of new 

 characters. The mutations occur fortuitously 

 as continuous or discontinuous, the result of 

 modifications in the germ plasm. If by chance 

 the variant, such as it is or by some change of 

 function, is adapted to fill a void in nature 

 and is able to reach this unoccupied place, it 

 has the opportunity to survive and to found a 

 new stock; if not, it remains in its original 

 surroundings or disappears. Formerly, when 

 unoccupied places were more abundant, in 

 fresh water, in marshes, in cracks and caverns 

 and on the earth's surface, in the air, in the 

 polar regions, conditions were favorable to the 

 differentiation of new species and new groups ; 

 now mutations have an ever-decreasing chance 

 of finding an occupied place in the fine bal- 

 ance of life already established, and evolution, 

 if not entirely checked, has at least become 

 much retarded. 



SPECIAL ARTICLES 



THE QUESTION OF VmPARITY IN FUNDULUS 



MAJALIS 



In a paper dealing with the process of hered- 

 ity in Fundulus hybrids' certain well-marked 

 differences were shown by the writer to exist 

 between the two reciprocal crosses. While a 

 large per cent, of the hybrids, obtained by 

 fertilizing the eggs of Fundulus heteroclitus 

 with the sperm of F. majalis, hatched and, in 

 some cases, throve for months after hatch- 

 ing, the embryos of the reciprocal cross {F. 

 majalis eggs fertilized with F. hetero- 

 clitus sperm) developed well for about two 

 weeks and then ceased to grow. These em- 

 bryos developed from the larger eggs of 

 the larger species, yet reached a maximum 

 size only equal, on the average, to that 

 of the just hatched young fish of the smaller 

 species, F. heteroclitus. Although morpho- 

 logically sufficiently advanced, they never 

 hatch, but remain stranded on a large yolk 

 mass which they seem incapable of assimila- 

 ting. 



These and other peculiarities of cross-bred 

 ' " Tlie Process of Heredity as Kxliibited in the 

 Development of Fundulus Hybrids," Journal of 

 Experimental Zoology, Vol. V., No. 4. 



