Ill 



LIVING MATTER 81 



Diueur found that the leucocytes of the blood also exhibit 

 galvanotactic properties with a marked preference for the anode. 



A different form of kathodic and anodic galvanotaxis was 

 observed at the end of 1885 by Hermann. When a galvanic 

 current is passed through a vessel containing tadpoles or fish 

 embryos, these animalcules orientate themselves with' their long 

 axes in the direction of the lines of current so that the head faces 

 the anode and the tail the kathode. They remain in this 

 position as long as current is passing ; if its direction be reversed, 

 they face to the opposite direction, like soldiers at the word of 

 command. 



Verworn recognised another form of galvanotaxis in a ciliated 

 infusorium, Spirostomum ambiguum, which, when traversed by the 

 galvanic current, turns so that the principal axis of its body is 

 at right angles to the direction of the current. This he terms 

 transverse galvanotaxis. 



XII. The directive action of stimuli, particularly of those due 

 to light and temperature, is of special importance for marine 

 organisms. Scientific data in regard to the fauna and flora of the 

 ocean are at present scanty in comparison with our knowledge of 

 the terrestrial fauna and flora, but there seems reason to believe 

 that the variety and magnitude of the animal and vegetable 

 kingdoms of the ocean are incomparably greater than of those 

 upon the earth. The paucity of data in regard to life in the deep 

 sea is obviously due to the difficulty of securing such beings as 

 live at a depth of several thousand metres below the surface. 



Many expeditions have been organised for the purpose of 

 studying marine biology ; these are equipped with ponderous 

 dredges, and are intended to remain several months at sea in order 

 to collect with different kinds of apparatus, at various seasons of 

 the year, the organisms that exist at different levels or at the 

 bottom of the ocean. The most important have been the Challenger 

 Expedition, conducted by Murray and Thompson (1884), and the 

 Valdivia, conducted by Chun (1898-99), in different seas. In the 

 Mediterranean, Krupp, on the Maia and the Puritan, investigated 

 the pelagic fishes, the scientific results of this expedition having 

 been illustrated and published by S. Lo Bianco (1901-3). 



The distribution of organisms in the different strata of water 

 (bathymetric distribution, either in the vertical or the horizontal 

 direction) has been determined with a fair amount of accuracy 

 by the use of special contrivances, constructed ad hoc. Such 

 are the nets fitted with an apparatus enabling them to be closed 

 at any required depth (measured by the soundings), so that they 

 cannot, when pulled up through the supernatant strata of water, 

 enclose any animals from these higher levels. Some are draw-nets 

 weighted with heavy rings of iron or other metal, which fall to the 

 bottom and are pushed along, gathering up the living organisms 

 VOL. i G 



