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On the 1 2th December, 1879, I found large quantities of 

 Mussels to contain similar embryos, the weather at the 

 time being very severe. On December 3rd, 1880, I found 

 the same. The winters of 1879-80 and 1880-1 were excep- 

 tionally cold, so that it appears they are not dependent on 

 " heat and tranquillity " for their proper development. 



On the 25th of May, 1879, after a very severe winter of 

 about nine weeks' continuous frost, I found on one of the 

 beds under my charge several acres of brood Mussels, 

 about the tenth of an inch in length. In the spring of the 

 year 1879, and the spring of 1880, overwhelming quantities 

 of brood were found on the scalps on the east coast of 

 England, which might be measured by hundreds of acres. 

 There has not been a fall of spat since. 



I found a few Mussels containing spat this year as late 

 as the 3rd June ; they appear to spat every year, but the 

 spat does not always attach itself to the beds. It is 

 probably carried away by the tides. 



Where Mussel brood is found in thick and dense masses, 

 they will be three years before they are what is called 

 sizeable, that is, two inches in length ; but instances are 

 found near low-water mark where a few have become 

 isolated, and have grown much more rapidly. 



I do not think that Mussels will spat, or rather that the 

 spat will mature, in partially-salt water. The only places 

 where I have ever seen any young brood is where the water 

 has the same degree of saltness as the outside sea, which 

 on the east coast of England has a density of about IO26J ; 

 distilled water being 1000. Although it appears that salt 

 water is necessary at their birth, brackish water is better 

 adapted for fattening and growing, provided they are 

 covered with the tide at high water. I find by experience 

 that the most suitable degree of saltness of the water for 

 VOL. VI. C. X 



