8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



very standard we wish for comparison with frequency of identification 

 in the stomachs of collected wild birds. The general correlation of 

 these factors to be noted in the tables presented in subsequent pages 

 increases confidence in the value of the method.* 



Identifications of Animal Food 



To illustrate the way in which data was assembled, that for the 

 phyla may be given in rather more detail than is planned for the 

 balance of the report. The figures for number of species in the various 

 phyla are compiled from various estimates ^ of this nature ; the facts 

 that these are not strictly up-to-date nor anything like exact are of 

 no consequence in a field where only approximations may be hoped for. 



The subjoined table shows the estimates used for the number of 

 described species in each phylum and the percentage that figure bears 

 to the total number of animals known. 



Phyla of .Iniinals and the A'lDuhcr and Percentage of Species in Each 



Percentage 

 of species 

 Estimated in this 



number of phylum 



species amon? the 



Phylum known whole number 



Protozoa 8,000 1.4272 



Porifera 2,500 .4460 



Coelenterata 4,500 .8028 



Platyhelminthes 5,000 .8920 



Nemathelminthes 1,500 .2676 



Trochelminthes 500 .0892 



Molluscoida 1,700 .3032 



Echinodermata 4,000 7136 



Annulata 4,000 7136 



Arthropoda 418,250 74.6188 



Mollusca 61,000 10.8828 



Chordata 49,565 8.8427 



Totals 560,515 99-9995 



* Here may be mentioned the law demonstrated by Olaf Arrhenius (Journ. 

 Ecol., vol. 9, no. I, p. 99, Sept., 1921) that among plants " The number of species 

 increases continuously as the area increases." Since as a rule the number of 

 individuals also increases with the area, the parallelism between the number 

 of individuals and that of species is further confirmed. 



" Pratt, H. S., On the number of known species of animals. Science, vol. 35, 

 pp. 467-468, March 22, 1912. 



Henshaw, H. W., Number of species of living vertebrates. Science, vol. 36, 

 PP- 317-318, Sept. 6, 1912. 



Handlirsch, A., Die fossilen Insekten, pp. 1182-1188, 1908. 



