THE CELL IN HEREDITY 65 



The discovery of the various dyes and tissue stains afforded a 

 wonderful stimulous to the microscopic study of tissues as well as to 

 bacteriological studies. It is hard to conceive of much progress in 

 bacteriology without this aid. Dyes for staining protoplasm were first 

 prepared in 1868. The property of taking up a stain gave rise to the 

 invention of a number of new names for which scientists have as 

 usual drawn freely from the Greek. To designate that protoplasm 

 which stained deeply, we have the term "chromatin." The word 

 "achromatin'* has been applied to protoplasm," which will not absorb 

 the dye. Certain rod-shaped bodies situated within the nucleus, 

 which stain more deeply than any other portions are known as 

 "chromosomes." 



The Cell In Heredity — Within recent years the subject of here- 

 dity has claimed the attention of biologists and its practical applica- 

 tion has become of intense interest to the laity, advances in our 

 knowledge of heredity are already producing results. They have 

 revolutionized agricultural methods as shown in the marked improve- 

 ment of animals and plants. It is impossible of realization what are 

 the potentialities in regard to the improvement of the human race. 

 Eugenics is as yet in its infancy. The past ten years has witnessed 

 the production of voluminous literature on eugenics and its kindred 

 subject heredity. 



Smallwood in his latest work states that "Whatever may be 

 the ultimate analysis of the problem of heredity, there can be no 

 hesitation in stating that the transmitted characters exist potentially 

 in the protoplasm of the cell. From the egg of a robin only a robin 

 will develop, from the ovum of an oak only an oak will grow and dur- 

 ing the growth each follows its own successive developmental stages 

 even to the minutest details. It has been well said ^nature never yet 

 made two eggs or two sperms exactly alike.* The cells which give 

 rise to new organisms are the germ cells, sperms and ova. These 

 differ greatly in shape and size — some of the sperm cells being but 

 one one-hundred-thousandths the bulk of the ovum and yet the pa- 

 ternal characters are easily recognized in the adult. * * * The 

 cells of the body are divided into body plasm and germ plasm." Germ 

 plasm might be looked upon as the immortal in man in as much as it 

 is continuous. After the germ plasm has given rise to a new individ- 

 ual, some of it is left behind to participate in the formation of a new 

 offspring, so as Davenport puts it, "There is really no inheritance 

 from parent to child but^^rent and child resemble each other because 

 they are derived from the same plasm, they are chips of the same 

 old block; and the son is half-brother of the father by another 

 mother." 



As the cell has been called "The physiological unit," and proto- 

 plasm "the physical basis of life," the chromosomes have been proven 

 the physical basis of heredity. They are very definite and import- 

 ant organs. The number which make their appearance at each cell 

 division is the same in all the cells of any given creature and is con- 

 stant for the cells of the members of any given species. 



"The remarkable fact," says Wilson, "has been established that 

 every species of plant or animal has a fixed and characteristic num- 



