380 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 

 1912. Biddul- Chaeto- Coscino- Rhizoso- Thalassi- Guinardia.Lauderia. 





phia. 



ceras. 



discus. 



lenia. 



osira. 







Jan. 



. 24,920 



7,342 



9,877 



22 







257 



189 



Feb. . 



. 36,885 



10,301 



10,034 



12 







105 



"*0 



Mar. . 



. 21,176 



3,977,292 



95,446 



525 



25 



162 



337 



April . 



. 21,869 18,365,750 



100,619 



36,464 



721,338 



3,158 



1,622,478 



May . 



. 1,072 



2,844,861 



14,586 22,008,744 



41,033 



2,789,433 



170,878 



June . 







67,543 



40,833,771 







5,919,429 







July . 







39,527 



56 



1,228 







158 







Aug. . 



11 



694,961 







13 















Sept. . 



. 4,131 



7,702,658 



1,677 



117,122 



3,978 



10,967 



8,944 



Oct. . 



. 5,827 



214,421 



11,914 



820 



57 



2,176 



29 



Nov. . 



. 25,714 



9,476 



5,436 











21 







Dec. . 



. 8,059 



1,106 



1,573 











141 







The above table sbows very clearly how the different 

 genera reach their maxima at different times, and how 

 Chaetoceras in spring gives place to Rhizosolenia and 

 Guinardia in early summer. 



Note on the Forms of Biddulphia present. 



Under the genus Biddulphia above we have, as in 

 previous years, recognised and recorded two " species," 

 B. mobiliensis and B. sinensis (see a and b, fig. 3), but 

 some variations in these forms have been noticed of late 

 upon which we wish to make some observations. 



In the photo-micrograph (fig. 3), a points to what 

 has been regarded hitherto as B. mobiliensis in our 

 district, and 6 to a typical example of B. sinensis. Our 

 B. mobiliensis undoubtedly approaches the form 

 " regia," regarded as a distinct though allied species by 

 Ostenfeld (Medd. Kom. Havunders., Plankton, Bd. I. 6, 

 1908). Gran, in the Diatomacea of the Nordisches 

 Plankton, unites these two forms as B. mobiliensis, and 

 we in recognition of the facts, as we conceive them, 

 consider that they should be known respectively as 

 Biddulphia mobiliensis, forma regia, Schultze, and 

 B. mobiliensis, forma sinensis. 



