180 PROF. W. A. HERDMAN ON THE DISTRIBUTION 
Laboratory, finds that as a matter of fact this form did appear in abundance 
in the collections of October 1909, within a month of the time when 
according to our records it reached Port Erin. Whether or not this species 
was brought accidentally by a ship from the far East, there is no doubt that 
it was not present in our Irish Sea plankton gatherings previous to 1909, 
but has been abundant since that year, and has completely adopted the 
habits of its English relations—appearing with B. mobiliensis in late autumn, 
Me 
Fig. 3.—Photo-micrograph of a plankton preparation showing (a) Biddulphia 
mobiliensis, forma “ regia,” and (b) B. sinensis. 
persisting during the winter, reaching a maximum in spring, and dying out 
before summer. | Biddulphia is generally the first Diatom to show a marked 
increase in early spring, and is responsible for the moderate rise in the curve 
which takes place in February or March. 
Our largest records of Biddulphia are as follows :— 
From three hundred thousand to over six hundred thousand per haul on 
several occasions between middle of March and middle of April in 1910 and 
1911, and towards end of April and beginning of May, 1916. 
From three hundred thousand to over seven hundred and fifty thousand on 
ten occasions between November 10th and 27th, 1911, 1914, and 1915. 
The highest monthly averages in the early spring months occur as 
follows :— 
February ... in 1907 and 1912. 
March — ... in 1910, 1911, 1914, and 1915. 
April x in 1908, 1909, 1913, and 1916. 
A second, usually slighter, maximum occurs in November, when the 
numbers are higher than in December and January ; but on three occasions 
