CH. Ill] LIFE IN THE SEA 55 



sea Clam/' had shewn that life existed even at that great depth. 

 In 1839 the dredge — " an instrument as valuable to the naturalist 

 as a thermometer to the natural philosopher " — was being widely 

 used, but the apparatus for employing it in deep water had not 

 yet been elaborated. Forbes based his speculations on the results 

 of his own dredging, which was made in water which we should 

 now call " shallow," and since, like all men of an original turn of 

 thinking, he reasoned from the observations made by himself, he 

 so fell into the error of drawing large conclusions from insufficient 

 data. Although he stated his beliefs hypothetically they were 

 accepted widely and stated by others as dogmatically as a prioi^i 

 speculations of the time could be; and for a long time afterwards the 

 deep sea was regarded as lifeless because of the apparent im- 

 possibility of animated things living under the influence of 

 immense pressure, and in the total absence of light and air. Also 

 the zones of distribution suggested by Forbes were accepted 

 by reason of their practical convenience, and are indeed still 

 referred to in faunistic discussions. But the great voyages of the 

 middle of the century and after soon extended our knowledge of the 

 distribution of marine animals with respect to the depth of the sea, 

 and it was by-and-by conclusively proved that there was no region 

 of the sea bottom which was entirely devoid of life. 



In 1839 the dredge was the instrument of investigation of the 

 marine naturalist, and knowledge of marine life was practically 

 restricted to the animals which lived on the sea bottom and could 

 be captured by means of this apparatus. The fishes and other 

 larger animals living in the upper layers of the sea were, of course, 

 known, but the incredible abundance of marine life which the 

 tow^-net and microscope were to reveal was then still unsuspected. 

 Not until 1845 did Johannes Muller, the great anatomist and 

 physiologist, begin to study the pelagic life of the sea by means of 

 the examination of samples of sea water. This method of work 

 w^as soon superseded by the use of the tow-net, and the material 

 collected by this instrument at once afforded an inexhaustible field 

 for systematic zoological investigation, and for the study of the 

 development and life histories of the previously known bottom 

 living animals. Huxley, Haeckel and many other zoologists began 

 systematically to use the tow-net, and by the employment of this 



