PEEIOD AT WHICH CHAEACTEllS APPEAR. 21 7 



inlieritance with the two very important laws of homotopic 

 and conteviporxineous transmission by inheritance. We 

 understand by them the fact that changes acquired by an 

 organism during its life, and transmitted to its descendants, 

 appear in the same part of the body in which the parental 

 organism was first affected by them, and that they also 

 appear in the offspring at the same age as that at which 

 they did so in the parent. 



The law of contemporaneous or homochronous transmis- 

 sion, which Darwin calls the law of " transmission in 

 corresponding periods of life," can be shown very clearly 

 in the transmission of diseases, especially of such as are 

 recognized as very destructive, on account of their here- 

 ditary character. They generally appear in the organism 

 of the child at the time corresponding with that in which 

 the parental organism contracted the disease. Hereditary 

 diseases of the lungs, liver, teeth, brain, skin, etc., usually 

 appear in the descendants at the same period, or a little 

 earlier than they showed themselves in the parental organ- 

 ism, or were contracted by it. The calf gets its horns at 

 the same period of life as its parents did. In like manner 

 the young stag receives its antlers at the same period of life 

 in which they appeared in its father or grandfather. In 

 every one of the different sorts of vine the grapes ripen at 

 the same time as they did in the case of their progenitors. 

 It is well known that the time of ripening varies greatly in 

 the different sorts : but as all are descended from a sinGrle 

 species, this variation has been acquired by the progenitors 

 of the several sorts, and has then been transmitted by 

 inheritance. 



The laiu of homotopic transmission, which is most 



