INHERITANCE CARRIED BY GERM-CELLS 27 



to include all that the living creature is or has to start with in 

 virtue of its genetic relation to its parents and ancestors, then 

 it is plain that the physical basis of inheritance is in the fertilised 

 ovum. The fertilised egg-cell is the inheritance, and at the 

 same time the potential inheritor. What might be compared to 

 an inheritance of property as apart from the organism itself is 

 the store of food which may be inside the egg, or round about it. 



To the general fact stated in the preceding paragraph, a few 

 exceptions must be made e.g. for bananas which have no longer 

 any seeds, for potatoes which are multiplied by cutting, for the 

 drone-bees and summer green-flies who have mothers but no 

 fathers, and for simple unicellular organisms in which there is 

 no sexual reproduction ; but the exceptions are trivial compared 

 with the vast majority of living creatures, in regard to which 

 it is certain that each life begins in a fertilised egg-cell. 



An organic inheritance means so much, even when we use the 

 comfortable word potentiality, that, although we are quite sure 

 that the germ-cells constitute the physical basis of inheritance, 

 we may consider for a moment the difficulty which rises in the 

 minds of many when they are told that the egg- cell is often 

 microscopic, and the sperm-cell often only T7n ^ nnr th of the 

 ovum's size. Can there be room, so to speak, in these minute 

 elements for the complexity of organisation supposed to be 

 requisite ? And the difficulty will be increased if the current 

 opinion be accepted that only the nuclei within these minute 

 germ-cells are the true bearers of the hereditary qualities. 

 Darwin spoke of the pinhead-like brain of the ant as the most 

 marvellous little piece of matter in the world, but must we not 

 rank as a greater marvel the microscopic germ-cells which, 

 contained potentially all the inherited qualities of that ant ? 



From one microscopic egg of a sea-urchin cut into three, 

 Delage reared three larvae. In another case he reared an embryo 

 from -g^th of an egg. Twin animals are often developed from 

 one egg. Wilson obtained quadruplets by shaking apart the 



