SEA-FISHERIES LABORATORY. 181 



were only about one million in that first year of work. From 

 1904 onwards the numbers have been much larger, and we 

 have records for each year of the quantities dealt with and of 

 the dates when the first fertilised eggs were seen, when the 

 various batches of eggs were placed in the hatching boxes 

 and when the larvae were taken out to sea. 



Systematic intensive study of the plankton in Port Erin 

 Bay was commenced in 1907, but previous to that, although 

 frequent plankton gatherings were taken for the use of those 

 working at the Biological Station, no statistics were kept. 

 Consequently, complete series of figures for a comparison of 

 the dates for fish larvae and phyto-plankton can only be given 

 for the fourteen years from 1907 to 1920 inclusive — and these 

 show a certain amount of correspondence and also a certain 

 amount of divergence. 



It may be objected that our data in regard to the fish eggs 

 and larvae may possibly have been affected by artificial con- 

 ditions, and so do not necessarily agree with the state of affairs 

 in the sea outside. That point has been carefully considered 

 and probably need not be regarded. The fish pond at Port 

 Erin receives water from the sea daily, and although the 

 temperature* of the water differs on occasions from that of 

 the bay the differences do not seem to be so great or so constant 

 as to affect the results. Temperatures in both pond and sea 

 have been taken twice daily (at 9 a.m. and 4 p.m.) for a number 

 of years, and although in summer the pond is warmer than 

 the open sea, and in winter colder, there seems to be no further 

 constant relation, the temperature of the pond being 

 especially in spring when the spawning is in progress — some- 

 times a little higher and sometimes a little lower and sometimes 

 the same as that of the sea. There is on occasions, however, in 

 spring a distinct difference in the alkalinity, the pond wain- 



* A. Dannevig has shown that there is a close relation between the 

 temperature of the sea and the quantity of eggs produced by the Ball in a 

 hatchery or pond — the intensity of the spawning increasing with every rise 

 of temperature (see Canadian Fish Egg* and Larvae, Ottawa, L918) 



