136 SECRETS OF ANIMAL LIFE 



to be compared, as Professor Brachet says, to a 

 harlequin's coat, composed of non-interchangeable 

 pieces. For a part of an egg is often as good as the 

 whole, in the early stages of development at least; 

 and a relatively large piece of the ovum may 

 often be cut off without doing the future embryo 

 any harm. Besides the nutritive yolk, which the 

 egg usually builds up from materials furnished by 

 the parent, it elaborates, as M Faure Fremiet 

 has shown in a unique research, a variety of other 

 chemical substances which are among the building- 

 stones of future structures. And besides these 

 bodies which the egg-cell makes for itself, there are 

 often ab initio others, with weird names, such as 

 mitochondria, which are regarded by many as 

 definite inheritance-vehicles. 



Lying in the midst of the complex cell-substance, 

 which often shows an intricate microscopic structure 

 (reticular or otherwise), there is a nucleus a mi- 

 crocosm within a microcosm. For inside this nu- 

 cleus there are all sorts of things, notably a definite 

 number of readily stainable bodies or chromo- 

 somes, which again may be resolved into beads of 

 chromatin embedded on pieces of a transparent 

 (linin) ribbon. The number of these chromosomes 

 is definite, e.g. 24 for mouse and lily, and each cell 

 throughout the whole body usually adheres to the 

 characteristic number. So each species, like the 

 Beast, has its number. Some say that a white man 

 has 47 and a white woman 48, and a negro only 22 ; 

 but in case any political advantage be taken of this 



