SEA-FISHERIES LABORATORY. 149 



The Shell. 



The length of each shell is found in cms., the measurement 

 being from the umbo to the extreme rounded portion of the 

 posterior edge. The shell is composed mainly of carbonate 

 of lime ; there is no trace of phosphate of lime. Iron is present 

 and seems to be connected with the blue colour of the shell. 

 This colour in mussel-shells is not uncommonly segregated 

 into stripes and bands, the remainder of the shell in such cases 

 being practically colourless. Pieces of shell with little colour 

 give feeble reactions when tested for iron, whereas the coloured 

 portions give very decided reactions. The shell also gives the 

 destructive flame reaction for strontium, and since this suggests 

 one of the ultimate destinations of strontium brought down 

 by rivers and streams, it will be interesting to examine other 

 mollusc shells, and calcareous alga 3 , to ascertain whether its 

 presence in these is general. 



Shells with the periostracum have been taken from each 

 sample and powdered in an iron pestle and mortar. After 

 obtaining the water content by weighing powder before and 

 after drying, the samples have been stored, and now await 

 quantitative estimation of carbonate of lime and iron to see 

 if there are any significant changes in the percentages through- 

 out the samples. 



Estimation of Fats. 



In the estimation of fats, 0-5 to 1 gramme of the powdered 

 mussel -flesh was taken from each sample and the extraction 

 carried out in a Soxhlet apparatus, carbon tetrachloride being 

 used as solvent. Whatman's fat-free extraction thimbles were 

 used, and these were cut down, so that when fitted into a 

 numbered weighing bottle, the lid of the latter could be 

 replaced hi position. By excluding air as much as possible 

 in this way, subsequent weighings were done with greater ease 

 and accuracy. 



The weighing bottle containing a cut-down thimble, a 

 plug of cotton wool, and also a Swedish filter paper, was first 



