SEA-FISHERIES LABORATORY. 287 



4. Thus, the Diatoms take on an enormous develop- 

 ment in early spring, and reach their maximum in April, 

 then die down during the summer, and may rise again to 

 a second but much less important and less constant 

 maximum in autumn. It must be borne in mind, however, 

 that the species, and to some extent the genera, that form 

 the autumn increase {Chaetoceros subtile and species of 

 Ehizosolenia) are quite different from those present in 

 gpring {Chaetoceros contortum and species of Thalassiosira). 



5. The Dinoflagellata rise to a maximum later than 

 • the Diatoms, and may have a second period of sudden 



increase in the autumn if weather conditions are 

 favourable. 



6. The Copepoda attain to their greatest develop- 

 ment in early summer after the Diatoms have died down, 

 and again in late autumn (October) they follow the 

 phytoplankton. As a rule a haul rich in Copepoda has 

 few Diatoms, and vice versa ; but the Copepoda do not, 

 like the Diatoms, present great maxima and marked 

 depressions. Even when both groups are present in the 

 plankton we frequently find that they are in different 

 zones ; for example, in some of the April hauls in 

 1907 the Diatoms were markedly on the surface and the 

 Copepoda below, while later in the year these positions 

 were reversed. 



7. The distribution of particular Copepoda (Calanus, 

 Anomalocera, Microcalcauis, Centropages, Tcmora, etc.) has 

 been discussed, and for the full results we must refer to 

 the body of this report. Calanus, Centropages and Temora 

 are present throughout the year ; Anomalocera appears in 

 our district in spring ; Microcalanus in late autumn 



8. Similarly the conclusions arrived at in regard to 

 the distribution of Sagitta, Tomopteris, the Cladocera, 

 0?'7copJeura, Cirripede Nauplii, and various other larval 



