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Show 392 RUDIMENTARY ORGANS. [CHAP. XIII. ments represent wings. Rudimentary organs sometime~ retain their potentiality, a?-d are merely not developed· this seems to be the case w1th the mammre of male mamInals for many instances are on record of these organs havi~g become well developed. in full-grown males, and having secreted 1nilk .. So agmn ther~ are normally four developed and two rud1mentar:y teats 1n the udders o~ tho O'enus Bos but in our domestic cows the two sornetimes become de~eloped and give mille I-r; individual plants of the same species the. pet~ls sometimes occur as mere rudiments, and sometimes In a well-developed state. In plants with separated sexes, the male flowers often have a rudiment of a pistil; and Kolreuter found. that b:y crosshlo' such male plants with an hermaphrodite spec1r.s, the ru~iment of the pistil in. the hybrid offspring :vas much increased in size · and this shows that the rudiment and the perfect pistil' are essentially alike in nature. . An organ serving for two purposes, may becom~ rudimentary or utterly abor~ed for one, eve~ the more Important purpose; and remain perfectly e~~Ie-r;t for the other. Thus in plants, the office of the pistil 1~ to allo·w . the pollen-tubes to reac~ ~he ov~les protec~ed In the ovanun1 at its base. The pistil consists of a stigma supported on the style ; but in some Compositre, the male flo~e~s, which of course cannot be fecundated, have a pistil, which is in a rudimentary state, for it is not crowned with a stigma · but the style remains well developed, and is clothed ~ith hairs as in other compositre, for the purpose of brushing the pollen out of the ~urrounding anthers. Again, an organ may become. r"?-dimen~ary f?r its proper purpose, and be used for a distln~t obJect: m certain fish the swim-bladder seems to be rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung. Other similar instances could be given. Rudimentary organs in the individuals of the same species are very liable to vary in degree of d~velopm~nt and in other respects. Moreover, in closely allied spemes, the degree to which the same organ has b~en rendered rudimentary occasionally differs much. This latter fact 0BAP. XIII.] RUDIMENTARY ORGANS. 393 is well .exempl!fied in the state of the wings of the female moths In certain group.s .. Ru~imentary oro-ans 111a be utterly aborted; and this Impbes, that we -&'nd in ~n animal or plant no trace of an organ, which analoo-y would !ead us to expe~t ~o.find, and which is occasiona~ly found Ill monstrous I~div~duals of the species. Thus in the s~apdragon (a~tirrhinun1) we generally do not find a rudiment of a ~fth stamen ; b~t this may sometimes be seen. In traCing the hornologws of the same part in different mernbers of a class, nothing is more common or mo.re.necessary, th~n the use a:1d discovery of rudime~ts. This IS well shown In the draWings given by Owen of the bones of the leg of the horse, ox, and rhinoceros It is .an iinportant .fact that rudimentary organs, such as teeth In the upper Jaws of whales and ruminants can often be detect~d in the e~bryo, but afterwards wholly disappear. It IS also, I beheve, a universal rule that a rudim~n~a:y part o~· organ is of greater size relatively to the adJOining parts In the embryo, than in the adult · so that the organ at. this earl:y age is less rudimentary, or even cannot be sa~d to be In any. deO'ree rudimentary. Hence, also, a rud1mentarv organ In t~e adult is often said to have reta~ned its eiT;br1onic condition. ' . I have now given the lead.Ing facts with respect to rudimentary or~ans. ~ reflecting on them, every one must be st;ruck With astonishment : for the same reasoning power w?~ch tells us plainly th~t most parts and organs are exquis.ltely adapted for certa;In purposes, tells us ·with equal pla_1nness that these rudimentary or atrophied organs, are Imperfect and useless. In works on natural history rudimentary organs are generally said to have been created "for the sake of symmetry," or in order "to complete the scheme of nature;" but this seems to me no explanation, merely a restatement of the fact. Would it be th?u~ht sufficient to say that because planets revolve in ellipt~c courses round the sun, satellites follow the same course round the planets, for the sake of symmetry, and t~ complete the scheme of nature? An eminent physiologiSt a~counts for the presence of rudimentary organs, by supposmg that they serve to excrete matter in excess or 17* ' |