244 THE SEAS 



from that of the previous months. Under the influence 

 of the benevolent rays of the sun, the tiny floating plants, 

 the diatoms, thrive and multiply exceedingly. Each 

 single-celled plant divides in half within the space of a day, 

 the two cells thus formed reproduce in turn to give rise to 

 four, so that in the course of a week or a fortnight their 

 numbers have risen prodigiously. If we draw our tow net 

 through the waters of the sea in spring we find that its 

 meshes become clogged with these little diatoms, and, 

 although singly almost invisible to the naked eye, they now 

 tinge the surface of the net green, so countless are their 

 numbers. Then indeed is the pasturage of the sea most 

 rich. 



Just about this time too there is a veritable outburst of 

 animal life in the plankton. In the early months of the 

 year a great number of all kinds of animals start to breed. 

 As we have already mentioned, there are few animals 

 around our shores whose early days are not spent drifting 

 freely in the water layers. The presence of these temporary 

 members of the plankton becomes very noticeable in April, 

 when a tow net catch will be found to consist almost 

 exclusively of these babies of the sea. There will be 

 larval stages of starfish, molluscs, worms and Crustacea 

 (Plate 87). Close around the rocks are amazing swarms 

 of the minute free-swimming young of the acorn-barnacle 

 which covers the surface of the rocks between tide marks 

 (Plate 87). Now is their time to enjoy a free life, for within 

 a month, they will have fastened themselves to the rocks 

 by their heads, there to remain kicking food into their 

 mouths with their feathery legs until they die. Further 

 from the shore, stretching over mile upon mile of water 

 are the young of that ubiquitous plankton copepod, the 

 Calanus, and mingled with them are the young of countless 

 other closely allied but smaller species. Young fish, too, 



