46 THE INORGANIC CONSTITUENTS OF MARINE INVERTEBRATES. 



The analyses, by Mr. Steiger, are as follows: 



Analyses of lobster shells. 



SiOj 



(Al,Fe)A 



MgO 



CaO 



PA 



SO, 



Ignition 



CO2 needed 



Organic matter, etc 



1. Small lobster. 



Claw. 



0.18 



2.35 

 27.04 



3.82 



.40 



63.60 



Cara- 

 pace. 



0.18 



1.96 

 26.55 



2.79 



.37 



64.90 



97.39 

 17.48 

 46.12 



95.75 

 18.06 

 46.84 



2. Medium lobster. 



Claw. 



0.17 



2.55 

 23.08 



6.70 



.59 



64.58 



97.67 

 14.39 

 55.19 



Cara- 

 pace. 



0.30 



1.80 

 23.53 



4.07 



.43 



68.72 



98.85 

 16. 45 

 52.57 



3. I/arge lobster. 



Claw. 



0.14 



2.35 

 21.89 



6.06 



.61 



66.32 



97.37 

 13.81 

 52.51 



Cara- 

 pace. 



0.24 



1.76 

 21.09 



4.48 



.58 



69.49 



97.64 

 14.03 

 55. 46 



Reduced analyses of lobster shells. 



Here again our suspicions were verified. In each case the large claw is more highly mag- 

 nesian and phosphatic than the carapace, and the increase in magnesia and phosphorus in 

 passing from youth to age is manifested. This last variation is more clearly shown by averaging 

 together the two analyses for each lobster, as follows: 



Average analyses of lobster shells. 



MgCOj. 

 CaCOj. 

 CajPjO 

 CaSO, . 



1. Small. 



9.27 

 75.69 

 13.45 



1.24 



2. Medium. 



9.70 

 68.02 

 24.92 



1.85 



3. Large. 



9.88 

 61.01 

 26.35 



2.32 



It is also worth noting that the proportion of calcium sulphate increases regularly, which 

 indicates that it is a definite constituent of the lobster shells and not a mere impurity. 



From these variations in the composition of lobster shells, all from a single locality, it 

 seems clear that in any future investigation of the same sort relative to crustaceans samples 

 of the entire shells should be analyzed and only adult specimens should be studied. Only 

 under such conditions will it be possible to determine whether regularities exist like those which 

 have been observed in other series of organisms. 



