THE CELL 



23 



salivary glands of Drosophila. (These chromosomes are enor- 

 mous in size and therefore excellent material for study.) He 

 finds that each chromosome has a definite and constant mor- 

 phology; it is made of segments with bands which entwine the 

 achromatic matrix. The pattern of bands and lines is constant 

 to an extraordinary degree so that it is possible to locate "genes," 

 or loci which stand for definite morphological characters (Fig. 15). 

 The importance of chromosomes is evident in a number of 

 ways; thus, every organism has a specific number. Man has 48 

 (female 48, male 47); the fruit fly, 8; and corn, 24. Japanese 



%»r 



Fig. 15. — Chromosome pattern showing loci (bands) of the hereditary deter- 

 miners or genes. {From T. S. Painter.) 



botanists (Kuwada, Morinaga, et al.) have been particularly 

 diligent in counting chromosomes and have found that there are 

 16 in the onion, 12 in rice, 24 in lily, 16 in one species and 24 in 

 another species of crocus, and 30 in tea. The behavior and con- 

 stitution of chromosomes are among the most fundamental of 

 problems with which the biologist has to deal in his study of living 

 matter. What we are and what we do are determined in great 

 measure by our chromosomes. They carry most, if not all, of 

 our hereditary characters. 



D. H. Wenrich discovered anatomical evidence of the indi- 

 viduality of the chromosome; this permits distinguishing them 

 and supports the concept of their continuity from generation to 

 generation. He observed the linear arrangement of particles 

 (chromomeres) in them. This is in harmony with the present-day 



