38 

 GERM-CELLS. 



fN order that full significance be attached to the discoveries 

 made by Dr. John Beard in the course of his embryological 

 researches, it will be necessary — or at least convenient — to 

 review briefly some of the generally accepted views regarding 

 the subjects treated ; it would of course be quite impossible in 

 one brief paper to refer to them all, neither, indeed, is it 

 necessary ; it will be sufficient in many cases simply to 

 note in passing the new light thrown upon them by Beard's 

 work. 



Let us first get a clear idea of what is understood by the 

 term germ-cells. 



Germ-cells are unicellular bodies borne by the gametophyte 

 of plants and the gametozoon of animals, and borne for the 

 most part in specially adapted receptacles. 



Germ-cells are of two forms, viz., eggs or germs, and 

 sperms; their function is reproduction, one sperm uniting with 

 one germ setting in motion that wonderful and mysterious 

 development that eventually culminates in the reproduction of 

 a plant or animal similar to that which gave rise directly or 

 indirectly to the germs and sperms. Thus it follows that all 

 the cells of any multicellular organism must have arisen from 

 the body of the united germ and sperm — fertilized egg — known 

 as a zygote. 



It is generally considered that the most important part of 

 the zygote is the chromatic material of the nucleoplasm. This 

 chromatic material is of course derived from the germ and 

 sperm. 



Here, note must be taken of the phenomena of mitosis; 

 all cells are derived from other cells by division. Cell division 

 is eff'ected by one of two methods : (a) direct division, known 

 as fission ; (h) indirect division, or mitosis. 



It is the indirect method only that claims our present 

 attention. During mitosis the chromatic material of the 



