Annual Meeting.] 228 [May 6, 



win and others. The increase of bulk and weight by growth in 

 proportion to the amount of food taken by the organism can be 

 illustrated in a series of the embryos of plants or of the chick, 

 ; showing the absorption of the store of food in the seed or yolk and 

 .the corresponding increase in size of the plant or animal. The effects 

 of use upon the forms of the teeth, and upon the structure and forms of 

 the bones, and series of specimens showing the most remarkable 

 results of experimentation such as Semper's on Lymnaea, and 

 Schmankewitsch's upon Artemia and Branchipus can be used advan- 

 tageously. Many parasites also show the effects of the habits of 

 life, and the correlative modifications which are produced in the 

 organism, by changes in their immediate surroundings. 



The subdivision wdiich represents the secondary, or organic 

 causes of change is more difficult on account of the confusion 

 which still exists in the minds of naturalists with regard to the law of 

 natural selection. We think, however, that examples of the action 

 .and reaction of organisms upon each other are obtainable from the 

 following sources : the numerous cases of mimicry between ani- 

 mals and plants inhabiting the same locality will furnish some of 

 ■ these, and others are to be found by a judicious selection of plants 

 and animals which depend upon each other for food and fertiliza- 

 tion. We shall also make an effort to exhibit in this collection 

 clear examples of the broader effects of natural selection, such as 

 the preservation. of advantageous differences, taking as examples 

 some of the clearest instances described by Darwin and some fossil 

 examples worked out by the curator. 



Mineralogy and Geology. 



Prof. W. O. Crosby has spent a proportion of his time during 

 the past year in remodelling the Guide to the Mineralogical Col- 

 lections of the Society. This is now completed and has been 

 approved by the Council and ordered to be printed at the expense 

 of the Museum appropriation. 



The accessions for the year include 120 mineral specimens, 

 which have been added chiefly to the New England Collection, and 

 300 specimens of rocks, which have been about equally divided 

 between the New England and general collections. 



These accessions, with the exception of the New England rocks, 

 .have been catalogued and mounted bj^ Professor Crosby assisted 



