NATURAL HISTORY OF THE MUSSEL 49 



We may, however, expect spawning to take 

 place generally after April, and to be most 

 abundant in June. At the same time it must be 

 remembered that a late summer commonly pro- 

 longs spawning through July, and that spat has 

 frequently been observed in the early part of 

 August. Spawning, once commenced, is much 

 influenced by weather. Favourable conditions 

 may extend the time, so that the various in- 

 dividuals of a bed get rid of their full complement 

 of eggs and sperms, a ' heavy fall of spat ' being 

 the result ; or, the season may be brought to a 

 sudden termination, and the embryos already in 

 process of development much injured by the 

 sudden advent of cold weather and storms. The 

 opinion that intense heat is detrimental to the 

 spawning capabilities of mussels is held in some 

 quarters of France ; but the highest temperature 

 of our summers can only, I think, be considered 

 as advantageous, unless the scalps are left un- 

 covered by the tide for long periods. The same 

 influences also determine the rapidity with which 

 the spat becomes finally fixed. 



From observations made at St. Andrews by Pro- 

 fessor M'Intosh, and reported by him to the North- 

 Eastern Sea Fisheries Committee, we are able to 



D 



