THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 114. JUNE 1877. 



XLIV. — On the Variability of the Species in the case of 

 certain Fishes. Bj Dr. V. Fatio*. 



Several authors have of late years demonstrated the influ- 

 ence of the surrounding medium upon organisms, and indi- 

 cated in various particulars the variability of the species. 



The struggle for existence and natural selection especially 

 are no longer subjects of doubt with many zoologists. 



A change in such or such a condition of existence almost 

 always superinduces a parallel modification in such or such 

 an organ, the mode of action of which is more or less affected ; 

 and this first translation of the external influences necessarily 

 draws after it corresponding disturbances in several other 

 parts characteristic of the species. 



Darwin, in his work on the Origin of Species, gives the 

 name of correlative variation to this kind of reaction of a 

 modified part upon other corresponding parts, and demon- 

 strates sufficiently by numerous examples that the changes 

 which have taken place in an individual may be reproduced 

 and multiplied by heredity. Hackel distinguishes direct or 

 immediate influences, acting upon the individual, and indirect 

 or mediate influences, which only become perceptible by here- 

 dity. This latter author even devotes a Avhole chapter of his 

 ' Natural History of Creation' to this subject, under the title 

 of " Laws of Adaptation." 



* Trauslatecl by W. S. Dallas, F.L.S., from the ' Bibliotheque 

 verselle : Archives des Sciences,' tome Iviii. p. L'^.'). 



Uni- 

 Ann. c(; Mag. N. Hist. Ser. 4. Vol. xix. 30 



