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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![by tlie fact, that in Sigalion the elytra and dorsal cirri exist side by side on the same segment. Homologies of the Rami of the Appendages in Astacns.—The view taken by Professor Gegenbaur, as to the homologies of the parts of the appendages immediately following the month in Astacns, differs somewhat from that which is current in this country. In Fig. 122, p. 239, the mandible, two maxilhe, and three maxillipedes of the right side of Astacns flnviatilis are figured. This woodcut was kindly re-drawn for the English edition by the author, at my re(][nest, and gives a more complete outline of the parts in question, than does the older cut of the German edition. Throughout the series of appendages, three divisions are distinguished by the letters a, c, d. Taking the lowest figure first (the third maxillipede) we find the endopodite marked a, the exopodite marked c, and the letter d placed with the single epipodite (podobranchia, Huxley) to its inner side, whilst the double arthrobranchia (Huxley) not forming part of the appendage proper, but a distinct respiratory development, is seen on its outer side. In the next figure (the second maxiUipede), a indicates endopodite, c exopodite, and d, is placed close to the double arthrobranchia on its outer side, whilst the modified epipodite is seen to the inner side again, of this. In the figure of the first maxillipede, a is placed near the foliaceous endopodite, which has a detached outstanding segment, c near the filamentous exopodite, and d near the broad epipodite. The same explanation of the lettering holds good for the next appendage, the second maxilla. In the next appendage— the first maxilla—the absence of the letters c and d, indicates that the author regards the whole appendage as reduced to the representative of the foliaceous endopodite a of the two inferior appendages—a view with which few will disagree. In the case of the mandible, hoAvever, Professor Gegenbaur marks the “ j^alp ” with the letter c—considering, therefore, the basal piece of this appendage to represent the endopodite, and the palp to represent the exopodite. The more usual opinion on this matter is that the mandible, together with its palp, corresponds to the simple foliaceous fimt maxilla. The jointed palp, mounted on its solid basal biting-piece, cor- responds to the jointed endopodite a of the last maxillipede. The question of the presence or the absence of a representative of the exopodite in the Decapod’s mandible, is a matter of considerable importance in reference to possible comparisons between the gnathites of Crustacea and Tracheata. The actual development of the parts in question from the nauplius-form of appendage, must be the ultimate test of the homologies of their rami in the Crustacea. Blood-corpuscles of the Mollusca.—The statement on p. 375, that the form-elements of the blood are always colourless ” in the Mollusca, is one which I may be allowed to correct, since I have published an account of the blood-corpuscles of Solen legumen (Proc. Royal Society, Ho. 140, 1873), which, besides colourless amoeboid forms, comprise a vast number of](https://iiif.wellcomecollection.org/image/b21725263_0014.jp2/full/800%2C/0/default.jpg)
