ANALYSIS OF ORGANISMS 179 



was smaller than in the latter; the largest amount of ether extract 

 obtained from plant material was noted in the sample of diatoms. 



Moore, Edie, Whitley, and Dakin 15 analyzed several marine forms, 

 but their results are not comparable with those given in table 49 because 

 they removed the skeletons from the organisms which they analyzed 

 and used only the soft parts. 



Ash Analysis 



Some of the inorganic constituents of the ash were determined for 

 a few of these samples as indicated in table 50. The results shown in 

 this table are stated in percentages of the dry weight of the sample. 



Silica (Si0 2 ). Quantitative determinations of the silica were made 

 on the ash of most of these samples and the results are recorded in 

 table 49. The diatoms yielded the largest percentage of silica, namely, 

 30.78 per cent of the dry weight of the sample. Cladophora ranks 

 second with 7.1 per cent and the Ephemerid larvae are third with 3.85 

 per cent. One sample of Daphnia pulex contained 2.84 per cent of 

 silica. Excluding these four samples, the silica in all of the other ma- 

 terial amounted to less than two per cent of the dry weight, ranging 

 from nothing in the Gyrinids to 1.96 per cent in Myriophyllum. 



Iron and Alumina (Fe 2 3 and A1 2 3 ). The results for iron and alu- 

 mina are shown in table 50. The sample of Myriophyllum contains the 

 largest percentage of iron and alumina, namely, 4.35 per cent of the dry 

 weight, while one of the samples of Daphnia pulex gives 2.94 per cent. 

 In all of the other samples on which determinations were made, the 

 percentage falls well below two per cent of the dry weight, varying 

 from 0.1 per cent in Limnocalanus to 1.8 per cent in Cladophora. 



Phosphorus (P 2 5 ). The sample of Cladophora is the only one re- 

 corded in table 50 in which phosphorus pentoxide falls below one per 

 cent. In the other plant material the amount is distinctly larger than 

 one per cent of the dry weight. The maximum percentages are found in 

 the Cladocera, namely, the three samples of Daphnia pulex and Lepto- 

 dora. All of the Crustacea, in fact, show relatively large percentages of 

 phosphorus pentoxide; the Cladocera rank highest, the crayfish (Cam- 

 barus) and the amphipod (Hyalella) second, and the copepods (Cy- 

 clops and Limnocalanus) third. The leeches (Hirudinea) and the in- 

 sects average about the same as the copepods. 



Clarke and Salkover 16 state that phosphorus is an important consti- 

 tuent of the ash of two marine crustaceans; for the copepod Temora 

 longicornis they record 2.77 per cent of the dry weight as calcium phos- 

 phate (Ca 3 P 2 8 ) and for the small shrimp Thysanoessa inermis 7.68 



15 Biochemical Journal, Vol. VI, 1912, p. 291. 



18 Jour. Washington Acad. Sci., Vol. 8, 1918, pp. 185-186. 



