96 



LIFE IN THE SEA 



[part I 



the list of fishes the eggs of which have been taken in the tow-nets 

 here in the spring months. 



Simultaneously, the larvae of many benthic and planktonic 

 creatures appear in the tow-nets. The diagram below has been 

 constructed from observations of the same series of collections 

 as that from which the distribution of fish eggs has been made out, 



Jan. Feb. MarAf)rrAcry JuneJuly Aug.Set). Oct. Nov. De( 



Copepod nauplii . . . 



Ascidian larvae 



Balanus nauplii 



Balanus cypres 



Crab zoeae 



Diatoms (max.) 

 Plutei 



Crab megalopae 



Rhizosolenia 



Halosphaera 



Aurelia, Rhizosolenia 



Squilla 



Xoctiluca 



Fig. 23. The rough succession of some planktonic organisms in the 



sea off W. England. 



and it shews the appearance in the course of the year of the larvae 

 of some of the commoner animals of the plankton. Copepods are 

 now and have for some time previously been carrying egg-sacs, 

 and the eggs in these begin to hatch out so that the nauplii of 

 these Crustacea begin in January to appear in the plankton. But 

 they are not abundant, for the copepods produce comparatively few 

 eggs and, as a group, spawn over a prolonged period of time. We 

 find their nauplii in the sea until the end of May. Ascidian eggs 

 containing developing embryos are also observed at the beginning 

 of the year and last until the autumn. A more striking change is 



