38 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



We have data for many years (from 1907) in regard to the 

 phyto -plankton in the sea off Port Erin, bnt it is not easy to 

 determine exactly when, in the open sea, the pelagic fish-eggs 

 have hatched out in quantity. We have, however, at the 

 Port Erin hatchery, the records, extending back to 1904, of 

 the numbers of eggs obtained from the spawning plaice in our 

 pond, the dates of hatching and the temperature of pond and 

 sea taken twice daily — and it is probable that these larvae, 

 although hatched under a roof, afford some clue to what is 

 going on in the sea at the time. The whole matter is discussed 

 more fully in the Lancashire Sea-Fisheries Laboratory Report 

 for 1919, pp. 82-88, but as the enquiry was carried on at 

 Port Erin it requires this brief mention in the Annual Report, 

 and I wish to place on record that Miss Maisie Hobbins, B.Sc, 

 while working at the Biological Station in April, gave me 

 great assistance in abstracting and comparing the records of 

 phyto -plankton and of hatching, of temperatures of pond and 

 sea, and of dates of spawning and temperature of water. 

 The plaice spawning in our pond at Port Erin was unusually 

 early in 1920, some fertilised eggs being produced in January, 

 and the temperature records show that the average for the 

 preceding winter months was high compared with recent 

 years. The mild winter seems to be accompanied by early 

 spawning of the plaice. There were, however, fewer hours of 

 sunshine than the average recorded for the spring months, 

 and this may have affected the photo-synthesis and reproduc- 

 tion of the phyto-plankton as the diatoms were late in appearing 

 in any quantity. It is possible, then, that the early-hatched 

 larvae found insufficient food in the sea and that the " year 

 class " of such fish for 1920 may not be largely represented in 

 the commercial fisheries of the future. 



A careful comparison of our data for the thirteen years 

 (1907-19) shows that in nine cases (1907, 1910-12, and 1915-19) 

 the phyto-plankton in the sea preceded the hatching of the 



