. Evolution and its relation to religious thought . andgreater, until finally it so obscures the essential identity,that it requires the most extensive comparison in thetaxonomic series and in the ontogenic scries, to pick upthe intermediate links and establish the fact of commonorigin. In a word, whether they so originated or not, itis certain that the structure of articulate animals is ex-actly such as would be the case if all these animals weregenetically connected, and came originally from a primalform something like one of the lower crustaceans, or,perhaps, a marine worm. It will be best
. Evolution and its relation to religious thought . andgreater, until finally it so obscures the essential identity,that it requires the most extensive comparison in thetaxonomic series and in the ontogenic scries, to pick upthe intermediate links and establish the fact of commonorigin. In a word, whether they so originated or not, itis certain that the structure of articulate animals is ex-actly such as would be the case if all these animals weregenetically connected, and came originally from a primalform something like one of the lower crustaceans, or,perhaps, a marine worm. It will be best to take an example from about themiddle of the scale, where the two elements, viz., essen-tial identity and adajotive modification, are somewhatevenly balanced, and both traceable with ease and cer-tainty. Take, then, a cray-fish, a lobster, or a animal (Fig. 27) has twenty or twenty-one ringsand pairs of jointed appendages. The rings are someof them diminished, some of them increased in size. HOMOLOGIES OF THE ARTICULATE SKELETON. 117. Fig. 27.—Shrimp (Palaemonetes vulgaris). Sometimes several are consolidated ; sometimes severalare partially or wholly aborted. The appeadages aremodified in shape andsize, according to theirposition, so as to makethem s^yimming-appen-dages (swimmerets),walking - appendages(legs), eating-append-ages (jaws), and sense-appendages (antennas). For example, in the abdomi-nal region, or so-called tail, we have seven segments,all being perfect movable rings, each with its pair ofjointed appendages, except the last, or telson. Theappendages of the first ring (Fig. 28, B) are speciallymodified in the male as organs of copulation (B). Thenext four pairs are modified for swimmerets (D) andfor use as holders of the eggs in the female. The ap-pendages of the sixth ring (G) are broad and paddle-shaped, and, together with the telson or seventh ring(H), form the powerful terminal swimmer. Going,now, to the cephalo-thorax : in this either a large n
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Keywords: ., bookauthorlecontej, bookcentury1800, bookdecade1880, bookyear1888
