SOME ASPECTS OF ZOOLOGY 45 



separate germ-plasms, which may be similar, but may be 

 different, in respect of the " factor " in question. 



If they are similar, you will get a " pure line " in respect 

 of the particular character that the factor in the germ-plasm 

 evokes. But if they are different, then some of the offspring 

 will have characters produced by the paternal factor, others 

 will have characters produced by the maternal factor, and there 

 will be differences which may affect the well-being of indi- 

 viduals, and consequently give scope to the agency of selection, 

 whether man's selection or Natural Selection. 



It was the recognition of this fact that led Weismann to 

 attribute variation to " Amphimixis," by which term he 

 meant the mingling of the germ-plasms of two separate 

 individuals. 



I have used the term " germ-plasm." Do you all know 

 exactly what that term means ? For the sake of those who 

 may not know, I will try to give a brief explanation. 



You all know that an egg is capable of giving rise to a 

 chick. There is an immense difference in structure and in 

 " vitality " (if I may try to compress a large number of 

 phenomena into a single word) between the egg and the chick. 

 A fowl's egg, with its shell, its white and its yolk, is rather a 

 complicated thing. Let us take a simpler, a frog's egg, a 

 little spherical mass, no bigger than a shot. This, under 

 proper conditions, gives rise to a tadpole, and the tadpole grows 

 into a frog. And for still greater simplicity's sake let us take 

 a plant. It is a familiar fact that a flower has to be pollinated 

 or fertilised before it will set seed. Pollen is made up of very 

 minute grains, and leaving certain complications out of 

 account, we may call this the male germ. Deep down in the 

 pistil of the flower is the female germ, a minute single cell. In 

 fertilisation the pollen-grain sends down a tube to the female 

 germ-cell or ovum, and the substance of the pollen ( <$ ) is 

 mingled with the substance of the ovum ( $ ). The result 

 of this mingling of the substance, or " plasm," of these two 

 is that the plant ovum is stimulated to growth and produces 

 a seed (which is really the quiescent stage of a young plant), 

 and the seed when sown grows into a plant, which in turn 



