ipt re. pm 
OF DIATOMS AND COPEPODA IN THE IRISH SEA. 187 
point in September—the greatest recorded monthly average being 10,967 for 
September 1912. It is interesting to notice that according to Pavillard 
Guinardia flaccida is abundant in the Gulf of Lyons as late as October. 
Fro, 10.—Guinardia flaccida, from a photo-mierograph by A. Scott. 
TABLE 
showing the monthly averages of the selected Diatoms throughout a year, 
| | 
1912. | Biddulphia. Mation — Rhizosolenia, ees Guinardia. | Lauderia, 
|Jan..... 24,920 7,842! 9,877 | 22 0 957 189. 
Feb. .. 306,885 10,201 10,034 12 0 105 0| 
Mar. .. 21,176 8,977,292 95446 595 95 162 387 | 
Apr ..| 21,869 18,365,750 100,019 ^ — 36,464 721,338 3,158 1,099478 - 
May ..| 1,072 | 2,844,861| 14,586 29,008,744 41,083 | 2,789,438 | 170,878 
June .. 0 67,543 0 | 40,888,771 0 | 5,919,429 0 
Taly. 0 39,527 56 1,228 0 158 0 
Aug. .. 1 694,961 0 13 0 0 0 
Sept. ..| 4,181 | 7,702058. 1,077 | 117,122 | 3,978 10,907 | 89944 
De....| 6897 214,421) 11,914 820 57 2176 99 
Nov. ..| 95714 | 9476 5,486 0 0 21 0 
Dec. ..| 8,059 1,106! 1,578 0 0 141 2 
The above table shows very clearly how these important genera reach 
their maxima at different times, and how, for example, Chetoceras in spring 
(April) gives place to Rhizosolenia and  Guinardia in early summer 
(May and June). Curves can be drawn mentally from a glance at 
the columns of figures which will demonstrate the waxing and waning of 
the several types. 
vcr ee eee: 
