8o THE WONDER OF LIFE 



other than ammonia, nitrates and nitrites). The question 

 is, how much of this foodstuff there really is; and here 

 the doctors differ. It is quite possible that organs with a 

 large surface, notably gills, have a directly nutritive value. 

 Prof. Putter's strongest argument is simply that the solid 

 food-supplies taken in by various types e.g. sponge and 

 crustacean are not sufficient to account for the chemical 

 changes that are known to go on. But the comparative 

 physiology of marine invertebrates is still very young. In 

 any case we must not too hurriedly dismiss the idea that 

 there may be, especially in crowded zones, a sort of perma- 

 nent * stock ' to the sea-soup. Every one who has examined, 

 even with the fingers, the foam that is blown ashore from 

 a rich littoral region after a storm, will agree that 

 there may be much dissolved organic matter in the water. 

 But this is no matter for opinion. It remains to be seen, 

 by careful analysis and after elimination of all the plankton, 

 how far it is true that there is bread in the waters. 



Recent investigations at Port Erin Biological Station, 

 by Prof. Benjamin Moore and others, have not in the least 

 confirmed Putter's view. Of great importance beyond 

 doubt in the economy of the sea are the extremely minute 

 organisms of the l dwarf plankton,' so small that they 

 pass through the interstices of fine silk cloth (see 

 Fig. 34). 



There are very interesting seasonal variations in the 

 amount of the Plankton, the two maxima being in spring 

 and autumn. Waves of abundance follow one another 

 in a regular order ; thus there is usually to begin with 

 a great multiplication of Diatoms, then of Dinoflagellata, 

 and then of Copepods. The reasons for the seasonal varia- 

 tions are still being investigated, but there is indication 



