we are reasoning about animal life, and if the continuity of lives with one another is interrupted, the series terminates, just as the series between the ovum, the fœtus, the child, and the man terminates, at whatever stage it is interrupted by a cause that destroys the mysterious principle of life. It is therefore absolutely necessary to look for some proof which will show that in the supposed series of successive generations of animals out of antecedent types, by whatever gradations and in whatever space of time we may suppose the process of evolution to have been worked, there has been a continuity of life between the different types, a perpetuation of organism from organism, a connection of lives with lives. We now come to another supposed analogy, on which great stress is laid by the evolution school, and especially by Mr. Spencer. Individuals of the same family are found to be marked by striking peculiarities of structure, ancestral traits, which appear and disappear and then appear again, in successive generations. This is obviously a case where the "appropriate conditions" are all comprehended in the connection of life with life. When we trace the pedigree of a single man or any other individual animal back to a remote pair of ancestors, we connect together in an unbroken chain the successive generations of parents and offspring. If the chain is anywhere broken, so that direct descent can not be traced throughout the series, we can not by direct evidence carry the peculiarities of family traits any further back than the ancestor or pair of ancestors with which we can find an unbroken connection of life with life. We do indeed often say in common parlance that an individual must have a trace of a certain blood in his veins, because of certain peculiarities of structure, complexion, or other tokens of descent, even when we can not find a perfect pedigree which would show where the infusion of the supposed blood came in. But although it might be allowable, in making out the descent of an individual man or any other animal, from a certain ancestor or pair of ancestors, to aid the pedigree by strong family or race resemblance, even when a link is wanting, it could only be for the purpose of establishing a pedigree, a connection of lives with lives, that such collateral evidence could be resorted to. If by direct proof of an unbroken descent a full pedigree is made out, or if, when some link is wanting, the collateral proof from strong family or race resemblances is sufficient to warrant the belief that the link once existed, we might accept it as a fact that the individual descended from the supposed ancestors in a direct line, or that some peculiarity of blood came into his constitution at some point in the descent of individuals from individuals.[74]