REPORT OF NATIOiSrAL MUSEUxM, 1921. 79 



persons connected with the Department of Agriculture have borrowed 

 from the National Herbarium 44 lots of plants, aggregating 1,293 

 specimens. 



DISTRIBUTION AND EXCHANGE OF SPECIMENS. 



DujDlicates distributed to schools, colleges, and institutions aggre- 

 gated 2,925 specimens, of which 1,242 were in 8 sets of molluslvis, 

 regularly prepared for this purpose, and two sets of 91 fishes each 

 similarly prepared. 



A collection of about 500 glass eels, averaging in length 57 mm.' 

 was collected for and presented to Dr. Johannes Schmidt, of the 

 Carlsberg Laboratorium, Copenhagen, Denmark, to assist him in his 

 studies of the development of the eel. Of the alcoholic specimens of 

 the 17-3'^ear cicada, collected for the use of colleges and similar 

 institutions, as mentioned in last year's report, one lot of 100 speci- 

 mens was distributed this year. 



Exchanges to the number of 12,530 specimens were arranged, 11,926 

 being botanical. Of the 604 zoological secimens, the most important 

 exchange consisted of 149 bird skins, which were sent to the Museum 

 of the University of Michigan ; the remainder were disposed of by 

 the divisions of mammals, birds, reptiles, fishes, marine invertebrates, 

 and mollusks in small lots as exchanges with various institutions and 

 individuals. The largest exchanges of plants were sent to the New 

 York Botanical Garden, British Museum of National History, Mr. J. 

 Theriot, Le Havre, France, Gray Herbarium of Harvard University, 

 Field Museums of Natural History, California Academy of Sciences, 

 and the College de Longueuil, Quebec. The others, made up of sets 



of less than 500 specimens, were exchanged with 53 different insti- 

 tutions and individuals. 



TOTAL NUMBER OF SPECIMENS IN DEPARTMENT OP BIOLOGY, INCLUDING NUMBER OF DUPLICATE 



SPECIMENS. 



As explained in previous reports, the numbers given below can 

 only be approximately correct. It would manifestly be impossible 

 to count the specimens individually. The figures presented are based 

 upon previous estimates, the numbers received during the year being 

 added, and the specimens disposed of by gift's and exchange, or other- 

 wise expended, being deducted. It should be noted that this census 

 does not include the collections of mammals and birds in the custody 

 of the Biological Survey. 



Duplicates have not been segregated in several of the divisions 

 for various reasons, but more particularly because a large amount of 

 material has yet to be worked over monographically, so as to make 

 it safe to deplete the series. The figures furnished in last year's re- 

 port for the duplicates of fishes contained not only the number of 

 duplicates actually segregated but also a rough estimate as to the 

 71305°— 21 6 



