: TRANSACTIONS OF SECTION D. 829 
The above examples, selected almost haphazard, will suffice to illustrate the 
Theory of Recapitulation. 
The proof of the theory depends chiefly on its universal applicability to all 
animals, whether high or low in the zoological scale, and to all their parts and 
organs. It derives also strong support from the ready explanation which it gives 
of many otherwise unintelligible points. 
Of these latter a familiar and most instructive instance is afforded by rudimentary 
organs, 2.e., structures which, like the outer digits of the horse’s leg, or the intrinsic 
muscles of the ear of a man, are present in the adult in an incompletely developed 
form, and in a condition in which they can be of no use to their possessors; or else 
structures which are present in the embryo, but disappear completely before the 
adult condition is attained, for example, the teeth of whalebone whales, or the 
branchial clefts of all higher vertebrates. 
Natural Selection explains the preservation of useful variations, but will not 
account for the formation and perpetuation of useless organs; and rudiments such 
as those mentioned above would be unintelligible but for Recapitulation, which 
solves the problem at once, showing that these organs, though now useless, must 
have been of functional value to the ancestors of their present possessors, and that 
their appearance in the ontogeny of existing forms is due to repetition of ancestral 
characters. Such rudimentary organs are, as Darwin pointed out, of larger relative 
or even absolute size in the embryo than in the adult, because the embryo repre- 
sents the stage in the pedigree in which they were functionally active. 
Rudimentary organs are extremely common, especially among the higher groups 
of animals, and their presence and significance are now well understood. Man 
himself affords numerous and excellent examples, not merely in his bodily structure, 
but by his speech, dress, and customs. For the silent letter 5 in the word ‘ doubt,’ 
or the w of ‘ answer,’ or the buttons on his elastic-side boots are as true examples of 
rudiments, unintelligible but for their past history, as are the ear muscles he 
possesses but cannot use, or the gill-clefts, which are functional in fishes and tad- 
poles, and are present, though useless, in the embryos of all higher vertebrates, 
which in their early stages the hare and the tortoise alike possess, and which are 
shared with them by cats and by kings. 
Another consideration of the greatest importance arises from the study of the 
fossil remains of the animals that formerly inhabited the earth. It was the elder 
Agassiz who first directed attention to the remarkable agreement between the 
embryonic growth of animals and their paleontological history. He pointed out 
the resemblance between certain stages in the growth of young fish and their fossil 
representatives, and attempted to establish, with regard to fish, a correspondence 
between their paleontological sequence and the successive stages of embryonic 
development. He then extended his observations to other groups, and stated his 
conclusions in these words:' ‘It may therefore be considered as a general fact, 
very likely to be more fully illustrated as investigations cover a wider ground, that 
the phases of development of all living animals correspond to the order of succession 
of their extinct representatives in past geological times.’ 
This point of view is of the utmost importance. If the development of an 
animal is really a repetition of its ancestral history, then it is clear that the agree- 
ment or parallelism which Agassiz insists on between the embryological and 
palzeontological records must hold good. Owing to the attitude which Agassiz 
subsequently adopted with regard to the theory of Natural Selection, there issome 
fear of his services in this respect failing to receive full recognition, and it must not 
be forgotten that the sentence I have quoted was written prior to the clear 
enunciation of the Recapitulation Theory by Fritz Miiller. : 
The imperfection of the geological record has been often referred to and 
lamented. Itis very true that our museums afford us but fragmentary pictures of 
life in past ages; that the earliest volumes of the history are lost, and that of 
others but a few torn pages remain to us; but the later records are in far more 
satisfactory condition. The actual number of specimens accumulated from the 
more recent formations is prodigious; facilities for consulting them are far greater 
1 L, Agassiz, Essay on Classification, 1859, p. 115. 
