DEPARTMENT OF EXPERIMENTAL EVOLUTION. 133 



cessory restricting genes, this return selection should not accomplish any 

 genotypic change. Up to date these investigations include over 670 pedi- 

 greed families and bristle-counts from considerably over 71,000 flies." 



METHODS. 



As heretofore, considerable attention has been given to the develop- 

 ment of statistical methods suitable for dealing with problems in hand 

 and to calculating tables to facilitate computations. A memoir has 

 been issued, by Dr. Harris, on the calculation of intra-class and inter- 

 class coefficients of correlation from class moments when the number 

 of combinations is large. Tables to facilitate the calculation of osmotic 

 pressure and the mean molecular weight of solutions have been prepared 

 by Drs. Gortner and Harris. 



A note has been published in ''Science" on a new collecting pipette 

 which some of the supply firms have already expressed an intention of 

 figuring and listing in their catalogs. The pipette is useful in collecting 

 small objects in difficult places and especially in handling delicate 

 specimens. It was devised by Dr. Banta. 



Dr. R. A. Gortner has published a device for freeing a precipitate 

 from mother liquor when filtering by suction. 



CONSTRUCTION AND EQUIPMENT. 



MAIN BUILDINGS. 



During the year under review the buildings started in 1913 and 

 described in the last Year Book were completed as far as at present 

 contemplated. The power-house has been in satisfactory use since 

 December 1 and has demonstrated that it can heat the plant with 

 economy and efficiency. During the summer the steam pipes were 

 extended by our own workmen to the greenhouses and to the old 

 laboratory. The hot-water system of the greenhouse is now heated 

 by steam by means of a Griscom-Russell heater. The radiators of the 

 old laboratory have been united with the vacuum system. Since it 

 seemed probable that we should not at present use enough electric 

 power to warrant installing a generator, our plant has been connected 

 up with the street main, and lights put in the greenhouses and three 

 ground lights at points where they will be most useful on dark nights. 

 The air-conditioning apparatus, providing for control of temperature 

 and moisture, is about to be installed. 



MISCELLANEOUS. 



Six new concrete cold frames were installed, and steam-heating pipes 

 were placed in the concrete pigeon-house and connected with the animal 

 house. New concrete coal-bunkers were built into the hillside, and a 

 concrete retaining wall built back of the animal house. A second 

 concrete bridge w^as built over the ravine, a garage provided, a gas- 

 oline storage-tank installed, chemical laboratory furniture made, and 

 the library room enlarged. New out-door pigeon flies were erected and 

 numerous bits of fencing and cabinet work done. An electric fire-pump 

 was installed in the power-house and connected with the reservoir of the 

 artesian well. The drive to the laboratories was surfaced with stone. 



