96 THE WONDER OF LIFE 



In reporting on the free-living marine Nematodes 

 collected at Cape Eoyds on the Shackleton Expedition, 

 Mr. N. A. Cobb refers to the same problem of vigorous life 

 in extraordinary conditions. Himdreds of specimens, 

 males, females, and young, were taken from a mere thimble- 

 ful of the dredgings. They seem to be rather smaller 

 than species in warmer seas, but they do not seem to be 

 less prolific. ' It is hardly conceivable that the body 

 temperature of the marine polar species is higher than that 

 of the water in which they Hve, namely, near the freezing 

 point of fresh water, and yet, in spite of the freezing tem- 

 perature, and the long polar night, nematode protoplasm 

 seems to glide on through its mitosis dance to much the 

 same purpose as i£ bathed in equatorial light and ensconced 

 in the warm pools of tropical reefs.' 



Of detailed problems there is a long hst, but we must 

 be content with one illustration. It concerns the eyes 

 of fishes. When we take a series of fishes from various 

 depths, starting with the shore, we find that some of those 

 from moderate depths (300-600 fathoms) have very large 

 eyes, and it seems reasonable to interpret this as an adapta- 

 tion to the faihng fight. We also find that some of those 

 from great depths, of over 1,000 fathoms, have very small 

 eyes, and it seems reasonable to associate this with the 

 darkness. A useless eye will tend to dwindle, for the 

 individuals with least of it will get on best. But the difiiculty 

 is that, along with the abyssal fishes with very small eyes, 

 there are others which have very large ones. It is difficult 

 to see how both conditions can be adaptive. Two sugges- 

 tions have been made : that those abyssal fishes with 

 large eyes are relatively newcomers, in which the 

 dwindling process has not begun, or that they are 



