GENERAL BIOLOGY 66i 



valuable as stimulating the investigator to seek realities. And 

 reality, in the scientific sense, means a definite positive 

 mechanism, existing in the organism itself or in the surrounding 

 medium. The object of investigation is to understand these 

 mechanisms ; the leading idea may often prove an empty fancy 

 beyond the world of realities. 



In the second half of last century the investigations on the 

 history of the development of animals disclosed many organs 

 (for instance, rudimentary organs), the function of which in the 

 life of the organism could not be understood. According to 

 the Darwinian idea the development of species consisted in 

 innumerable minute changes. These changes were conceived 

 as being due to "chance," which to a certain extent seemed to 

 contradict the idea of " fit adaptations." 



The historical way of explaining the structure or occurrence 

 of organisms is, however, at present not considered contradictory 

 to the ideas of adaptation. Even Lamarck, as mentioned above, 

 thought that a species must exist for a very long time before 

 the effects of the influence of surroundings appear or disappear. 



As to the origin of variation it is now more and more 

 recognised that a comprehension is only to be gained by studying 

 the reaction of organisms against the influence of surroundings. 

 One may endeavour to ascertain these reactions by experiment, 

 by observing the changes taking place in the organisms when 

 subjected to altered conditions. In nature we may also observe 

 how the shape of individuals alters in various surroundings, and 

 how similar shapes reappear in similar environments. 



In recent times we note an increasing tendency to observe 

 animals in their natural surroundings, and during frequent ex- 

 peditions the influence of this tendency has been predominant. 

 In recent literature we may find many investigations and many 

 opinions, which remind us of the interest attached to these 

 problems about a hundred years ago. 



In the history of oceanic research nothing has possibly con- 

 tributed so much to the awakening of this interest as the 

 discovery of entirely different animal -communities living, on 

 either side of the Wyville Thomson Ridge (see Fig. io6, p. 124). 

 Atlantic forms occur to the south and Arctic forms to the north 

 of the ridge, corresponding to the very different thermal 

 conditions on either side.^ 



1 See Murray and Tizard, " Exploration of the Faroe Channel, during the summer of _iS8o, 

 in H.M.'s hired ship 'Knight Errant,'" Proc. Roy. Soc. Ediii., vol. x. p. 638, 1882 ; Tizard, 

 " Remarks on the soundings and temperatures obtained in the Faroe Channel during the summer 



