ANALYSIS OF ORGANISMS 171 



pentosans. These three analyses, therefore, seem to establish the fact 

 that Holopedium regularly possesses a much larger percentage of pen- 

 tosans than the other animal forms represented in table 49 ; the percent- 

 age shown in the table is the mean of the three determinations. Holo- 

 pedium differs from all of the other Cladocera in that its body is en- 

 closed in a large transparent, gelatinous case and the large yield of 

 pentosans suggests that this gelatinous covering may be the source 

 of these carbohydrates. 



The three samples of Leptodora showed a variation of more than 

 two per cent in their nitrogen content ; on an ash free basis the range 

 is from 8.35 per cent to 11.09 per cent of the organic matter. The 

 latter is the maximum percentage of nitrogen in the various samples of 

 Cladocera and it is also a little larger than the maximum in the Cope- 

 poda. The percentages of ether extract, pentosans, nitrogen free ex- 

 tract, crude fiber, and ash fall within the range of variations shown by 

 the various samples of Daphnia. The mean percentage of nitrogen free 

 extract and of ash is smaller in the Leptodora material, however, than 

 in the Daphnias. 



The percentages obtained for the organic constituents of the fourteen 

 samples of Cladocera are very similar to those noted in the five samples 

 of Copepoda as shown in table 49 ; the most striking difference is the 

 larger percentage of ether extract in Limnocalanus. As a whole the 

 samples of Cladocera yielded a much larger proportion of ash than 

 those of the Copepoda ; the maximum percentage of ash in the former is 

 more than four times as large as the maximum in the latter group of 

 Crustacea, while the minimum of the former is nearly one and a half 

 times as large as the maximum percentage of ash in the latter. 



Volk 12 records an analysis of another cladoceran, namely, Bosmina, in 

 which he found that 77.83 per cent of the dry sample consisted of 

 " muscle and other tissue," 10.66 per cent of fat or ether extract, 8.21 

 per cent of crude fiber or chitin, and 3.3 per cent of ash. (See table 

 51.) This result is similar to that shown by Volk for Eurytemora 

 which is referred to on a previous page; that is, apparently he de- 

 termined the ether extract, the crude fiber, and the ash, and then desig- 

 nated the remainder as "muscle and other tissue." The percentage of 

 fat or ether extract in Bosmina is the same as that in Holopedium, while 

 the percentage of crude fiber or chitin in the former is substantially the 

 same as that noted in three of the Daphnia samples. The percentage of 

 ash in Bosmina is much smaller than those noted for the various sam- 

 ples of Cladocera in table 49. 



Cambarus. Forty-four specimens of crayfishes belonging to the 

 genus Cambarus were collected and analyzed for the purpose of getting 



12 Verhand. d. Naturwis. Vereins in Hamburg, 3. Folge XV, 1907, p. 45. 



