ANALYSIS OF ORGANISMS 175 



The five copepod samples, in general, yielded a larger percentage of 

 ether extract than the insect larvae, the amount in Limnocalanus being 

 a little more than twice as large as the maximum in the latter samples. 

 In seven samples of Cladocera the percentage of ether extract fell below 

 the minimum in the insect larvae and three contained a larger percent- 

 age than the maximum in the latter. The crayfish sample yielded a 

 smaller amount of extract than the minimum of the insect larvae, 

 while the amphipods and the leeches corresponded closely to the 

 Anisoptera and Zygoptera respectively. 



The crude fiber and the nitrogen free extract in the insect larvae 

 came within the range of variation noted in the plankton Crustacea, 

 except that the percentage of nitrogen free extract in Chironomus ten- 

 tans exceeded that in any of the other samples of animal material. 



Three of the samples of insect larvae yielded about the same per- 

 centage of ash as the copepod samples, but the other five insect samples 

 gave a larger percentage of ash than the copepod material. About 

 half of the Daphnia samples, together with the crayfishes and the am- 

 phipods, contained a larger amount of ash than the maximum in the 

 insect larvae, while the worms and leeches yielded about the same per- 

 centages of ash as those noted in Corethra plamicornis and Chironomus 

 tentans. 



Gyrinidae. This sample consisted of adult whirligig beetles that 

 were obtained from the surface of the water. This material contained a 

 much smaller percentage of nitrogen than the insect larvae, yielding 

 only a little more than half as much as the maximum found in Corethra 

 punctipennls. The percentage of nitrogen in these beetles, in fact, is 

 smaller than in any other sample of animal material. 



The percentage of ether extract is much larger in the Gyrinids than 

 in the insect larvae, being from two to more than four times as large as 

 the percentages in the latter; it is exceeded only by the large extract 

 noted in Limnocalanus. 



Whirligig beetles have relatively large and thick wing covers of 

 chitinous material; as a result the percentage of crude fiber or chitin 

 is much higher in them than in most of the insect larvae, that in Ani- 

 soptera being nearest to it. On an ash free basis the percentage of crude 

 fiber in the Gyrinids is next to the largest obtained for the animal 

 samples, being exceeded only by Cambarus. 



The percentage of nitrogen free extract is relatively low in this sam- 

 ple of Gyrinids; only two samples of insect larvae and four of plank- 

 ton Crustacea have a lower percentage. 



This beetle material yielded an unusually small percentage of ash; 

 it is the smallest noted in any of the samples recorded in table 49. It 

 is only a little more than one-third as large as the minimum percentage 

 in the insect larvae. 



