176 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



AN INTENSIVE STUDY OF THE MAEINE PLANKTON 

 AROUND THE SOUTH END OF THE ISLE OF 

 MAN.— PART XII. 



By W. A. Herdman, F.R.S., Andrew Scott, A.L.S., and 

 H. Mabel Lewis, B.A. 



We had hoped to close this series of statistics and issue a 

 final report on this occasion, but pressure of other work has 

 rendered it impossible during the present year to undertake 

 the. necessary full discussion of our accumulated data and a 

 careful re- consideration of the results arrived at in these 

 interim reports. We deal, therefore, again with the observa- 

 tions and results of the past year only. 



The work during 1919 has been carried on in exactly the 

 same manner as in previous years, and 536 samples of plankton 

 were collected in the neighbourhood of Port Erin, and have 

 since been worked up in detail. These bring the total number 

 of samples for the 13 years' work, since 1907, up to 6,498. 



In addition to an average of six gatherings per week 

 throughout the year in Port Erin Bay, in the specially important 

 months of March, April, July, August and September, special 

 hauls were taken both in the bay and outside in the open sea 

 from the motor-boat " Redwing." The results have been 

 treated in the usual way, and the forms, lists, tables and graphs 

 are stored available for future reference. The following is 

 only a summary of the outstanding facts of the year. 



The vernal plankton maximum was again in May, and 

 the largest total catch with the standard net was 99 c.c, taken 

 on May 9th, 1919. The monthly average catch rises from 

 about* 3 c.c. in January and February, to 12 in March, 20 in 

 April, to the climax 36 in May, and then falls to 21 in June, 

 7 in October, and so down to the minimum of 3 again in 



* We give the nearest whole numbers. 



