CRUSTACEANS. 



45 



With the oxcej)tion of the banmcles the analyses of crustaceans show that they are definitely 

 phosjihatic, a fact that was already well known. They are also maf;;nesian. another fact that in 

 nearly all previous analyses had either been neglected or overlooked. The magnesia, however, 

 shows no such regularity with regard to temperature as has been established by our analyses of 

 alcytmarians and echinoderms. KripJiia, for example, a tropical form, is abnormally low in mag- 

 nesia; whereas ChlorideJla, also from warm water, is remarkal)ly high. In other analyses the pro- 

 portion of magnesium carbonate appears to be about normal, but unfortunately the records for 

 some specimens are defective as to precise lo(;alities and temperatures. Furthermore, the large 

 amounts of organic matter and water render the reduced analyses to some extent unsatisfactory. 

 This is especially true of anah^sis No. 9, in which the inorganic portion amounted to only 21 

 per cent. In reducing such an analysis the unavoidable analytical errors are multiplied, and 

 the percentages of magnesium carbonate, calcium carbonate, and calcium phosphate may be 

 uncertain by as much as 1 per cent each. In no case is the order of magnitude seriously changed, 

 hut the accurac}' of the figures is not what we should wish it to be. 



The irregularities in the magnesian content of the crustaceans led to a suspicion that they 

 might be partly due to differences in the age or maturity of the specimens that were analyzed. 

 In order to test this supposition we obtained, tlii-ough the kindness of Dr. H. M. Smith, Director 

 of the United States Bureau of Fisheries, the large claws of two lobsters {Honiarus) taken at 

 the station at Boothbay Harbor, Maine. One specimen was from a small lobster, the other 

 from a large one, but the actual size of each lobster was not given. The anah'ses, by George 

 Steiger, were as follows : 



Analyses of loister claws. 



Actual analyses. 



SiOj 



(Al. Fe),03 



MgO... 



CaO 



PA 



SO3 



Ignition 



COj needed 



Organic matter, etc 



SmaU. 



0.11 



1.68 

 30.60 

 '3.22 



' .4.T 



63.42 



99.48 

 22.66 

 40.76 



Large. 



0.43 



2.90 

 23. 81 



9.03 



.60 



62.44 



99.21 



18.17 

 44.27 



Reduced analyses. 



SiO^ 



(Al, Fe)20. 

 MgCOj....' 

 CaCOa 



CaaPA--- 

 CaSO^.... 



I 0. 19 ij 0, 81 



Small. Large. 



6.02 

 80.52 

 11.98 



1.29 



100. 00 



11.51 



64.37 



21.46 



1.8.5 



100.00 



The (lifTerences between these two analyses are very striking and confirmed our first 

 suspicion. In order to make the investigation more precise. Dr. Smith bad sent us from the 

 same locality, Boothbay HarboT, parts of thi-ee lobsters; one small, one mediiun, and one large. 

 The actual figures for each entire lobster were as follows : 



1. Small lobster: Length, SJ inches; weight, 10 ounces. 



2. Medium lobster; Lengti, llj inches; weight, 2 pounds. 



3. Large lobster: Length, 16^ inches; weight, 5i pounds. 



Furthermore, for each lobster a large claw and part of the carapace was supplied, so that 

 for each animal two analyses could be made. This last precaution was taken because it was 

 remembered that in two sea urchins it was found that the spines and the shell differed in 

 composition. Is an analogous difference between two parts of the same animal to be found 

 among the crustaceans ? 



