218 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 law of homochronous and homotopic 
transmission are fundamental laws of embryology, 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 curious; 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 offspring, 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 
