BIOLOGY. 325 



An almost equally complete set of samples has been secured in the vicinity 

 of Los Angeles, where diatom outcroppings are abundant and remarkably 

 diversified. Material of this kind was also collected at Monterey Bay and 

 in the neighborhood of San Francisco, as well as a few samples from Oregon 

 and Washington. 



During the trip lectures were given at various points on local diatom condi- 

 tions, as well as brief instructions and demonstrations of methods for diatom 

 study. 



The work at Washington has been handicapped for lack of adequate labora- 

 tory help. The study is a peculiar one; the financial reward is necessarily 

 small, and so far it has been impossible to find candidates willing to take the 

 position and gifted with the necessary interest in and talent for this field of 

 scientific research. The writer has therefore had to do most of the work of 

 preparation and study without assistance. The following is a short summary: 



The long-delayed report on the diatoms of the Philippine Islands, mentioned 

 in former reports, is now ready for publication. The study of the diatoms 

 of the Canadian Arctic Expedition is about completed. The material of the 

 Antarctic Expedition, sent out from Australia under Sir Douglas Mawson, 

 has been received, cleaned, and prepared for study and largely worked out. 

 It is proving to be very rich in genera and species, some of which are new. 

 As is the case each year, a good many samples of diatom material from 

 private parties, chiefly commercial houses, has been submitted to the labora- 

 tory for examination. This public service seems to be justified, although it 

 takes considerable time through the year; it has some scientific value, and the 

 information sought is practically unobtainable outside of this laboratory. 



In addition to the work of preparing and investigating diatom material, 

 the large collection of such material located at the U. S. National Museum, 

 together with prepared specimens, has been entirely reclassified during the 

 year on a plan which makes it available for the growing number of outside 

 workers who apply for information or for diatom supplies. Like all new fields 

 of research, the opportunities are much in excess of the facilities, but en- 

 couraging progress is being made. 



Morgan, T. H., A. H. Sturtevant, and C. B. Bridges, Columbia University, 

 New York. Study of the constitution of the germ-plasm in relation to 

 heredity. (For previous reports see Year Books Nos. 15-20.) 



In the course of the year about 20 new mutant types have been studied, and 

 at least 10 of these will prove useful for future work on the localization of the 

 genes in the chromosomes. None have fallen outside the four known linkage 

 groups. A new allelomorph at the white locus has been found, which makes 11 

 mutant genes at the locus, or 12 in all, counting the wild-type gene. The 

 evidence showing that this "nest of genes" is not due to close linkage, but to 

 independent mutation of the same wild-type gene, has been given elsewhere. 

 The significance of this evidence in its bearing on the "presence and absence" 

 hypothesis has not even yet been appreciated by workers in other fields. 



In the course of the last two years, the amount of the data bearing on the 

 location of genes in chromosome III has been approximately doubled. This 

 has necessitated the construction of a more complete "map," which is here 

 represented by a partial list of loci, with their distances from an arbitrarily 

 chosen locus at one end. The locations are based on the most usual types of 



