Elements of comparative anatomy / by Carl Gegenbaur ; translated by F. Jeffrey Bell ; the translation revised and a preface written by E. Ray Lankester.
- Lankester E. Ray (Edwin Ray), Sir, 1847-1929.
- Date:
- 1878
Licence: Public Domain Mark
Credit: Elements of comparative anatomy / by Carl Gegenbaur ; translated by F. Jeffrey Bell ; the translation revised and a preface written by E. Ray Lankester. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![tlie embryos of tbe higher Vertebrata^ but by-and-by disappear, are structures of this kind. Regarded alone they are inexplicable, for they neither lead to the formation of gills at any time, nor are they converted (with the exception of the anterior) into definitive organs of any other kind. Comparison shows us, however, that in a large division of lower Yertebrata these branchial clefts are important organs of respiration; and as we also know Yertebrata (Amphibia), in which the clefts function only for a time as respiratory organs, and close up later on, we are able to comprehend the branchial clefts of reptiles, birds, and mammals, as arrangements obtained by transmission from lower stages, which have lost their primitive function, and remain for a short time only—during foetal life. § 6. In the sum of the characters of the organisation, which inherit- ance passes on to an organism, we find, in consequence of what has been already pointed out, a greater or smaller number of arrange- ments, which pass on into the permanent adult stage of the organism without having any recognisable function in it. Such ]3arts are, as a rule, seen in a more or less atrophied and rudimentary condition, which they often do not acquire until the ontogeny has run its course. In the early stages of the ontogeny they generally agree in completeness with the other arrangements which obtained in the ancestral form from which they are derived. These rudi- mentary organs commence to atrophy the earlier in proportion as they were inherited earlier, in a palseontological sense; and, as a rule, disappear late when their origin is a relatively late one. The fully- developed form of the rudimentary organs is consequently to be found, in the former case, in widely separated species; in the latter, on the other hand, in species more closely allied. These organs are valuable objects, since phylogenetic relations can be very generally recognised by their aid. They show, too, how little physiological significance ought to be regarded in a morphological discussion; for in most of them a function is not to be made out at all, or, if it can be made out, is found to be quite different to the primitive one. § 7. Comparative Anatomy forms part of Ontogeny, inasmuch as it treats of the phsenomena of the organisation which appear in the course of the individual development of the animal; not only in relation to the complete stage of the organism, but in relation also to the definitive arrangements of other organisms. Comparative](https://iiif.wellcomecollection.org/image/b21725263_0039.jp2/full/800%2C/0/default.jpg)
