2l8 THE HISTORY OF CREATION. 



closely connected with the last mentioned law, and which 

 might be called the law of transmission in corresponding 

 parts of the body, may also be very distinctly recognized in 

 pathological cases of inheritance. Large moles, for example, 

 or accumulations of pigment in several parts of the skin, 

 tumours also, often appear during many generations, not only 

 at the same period of life, but also in the same part of the 

 skin. Excessive development of fat in certain parts of the 

 body is likewise transmitted by inheritance. Above all, it 

 is to be noted that numerous examples of this, as well as of 

 the preceding law, may be found everywhere in the study of 

 embryology. Both the la%u of ho'tnochronous and homotopic 

 transmission are fundamental laws of emhryologi/, or 

 ontogeny. For these laws explain the remarkable fact that 

 the different successive forms of individual development in 

 all generations of one and the same species always appear 

 in the same order of succession, and that the variations of the 

 body always take place in the same parts. This apparently 

 simple and self-evident phenomenon is nevertheless exceed- 

 ingly wonderful and cuiious; we cannot explain its real 

 causes, but may confidently assert that they are due to the 

 direct transmission of the organic matter from the parental 

 organism to that of the ofispring, as we have seen above in 

 the case of the process of transmission in general, by a con- 

 sideration of the details of the various modes of reproduction. 

 Having thus, then, considered the most important laws of 

 Inheritance, we now turn to the second series of phenomena 

 bearing on natural selection, viz. to those of Adaptation or 

 Variation, These phenomena, taken as a whole, stand in a 

 certain opposition to the phenomena of Inheritance, and the 

 difficulty which arises in examining them consists mainly 



