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Show 368. PROVISIONAL IIYPOTIIESIS C HAl'. XXVIL Muller remarks, the n.v er cray-fi s1 · 1 t heel under the same 1 rs 1a c . d t · . the younrr lobster has form which It ever afterwar s re ams' b·s under the divided legs, like a Mysis; the Palremon app~~1 , . form of a Zoea and Peneus uuder the N auphus-form' an~ how wonderfull; these larval forms differ from each other, rs k t t . 1· t 16 Some other crustaceans, as the nown o every nama JS • • d · t f th same r)omt an arnvo a same author observes, start rom e . 1 th 1 b t l·n the middle of theu development arc near y e same enc, u , . ,· ,· o· wr' d e1 y d'wf'.[!e rent f rom e ach other · Sti.l l more stiJ.l\.m. b. cases, could be given with respect to the Echmodermata. With tl~o M d · 11 fi h p 0e usrn or Je y- s es r .cessor· Allman ouserves, ''the classr- 1' • • " fication of the Hydroida would be a compar~tivel~ srm_rle " task if as has been erroneously asserted, generiCally-IdentiCal " medus~ids always arose from generically-i~enti~al polypoi~s ; " and on the other band, that gen~rical~y-rdentwal pol,~·pOids " always gave origin to generically-rde~twal ~edu.sOids. So, ::Jga·m , Dr.. Stretbill Wright remarks, "m. the hfe-h1story. of the ,, Hydroidrn any phase, planuloid, polypord, or medusOid, may " be absent." 17 Accordin<Y to the belief now generally accepted by our best naturalists, 0all the members of the same order or class, the Macrourous crustaceans for instance, are descended from a common progenitor. During their descent they have diverged much in structure, but have retained much in common; and this eli vergence and retention of character has been effected, tbou<Yh they have passed and still pass through marvellously diffe;ent metamorphoses. This fact well illustrates how independent each structure must be from that which precedes and follows it in the course of development. The Functional Independence of the Elements or Units of the Body.-Physiologists agree that the whole organism consists of a multitude of elemental parts, which are to a great extent independent of each other. Each organ, says Claude Bernard/8 16 Fritz MUller's 'Fiir Darwin,' 1864, s. 65, 71. The highest authority ou crustaceans, Prof. Milne Edwards, insists (' Atmal. des Sci. Nat.,' 2nd series, Zoolog., tom. iii. p. 322) on their metamorphoses di:fl'ering even in closely allied genera. 17 Prof. Allman, in ' Annals and Mag. of Nat. Hist.,' 3rd series, vol. xiii., 1SG4, p. 348; Dr. S. Wright, idem, vol. viii., 1861, p. 127. See also p. 358 for analogous statements by Sars. 18 'Tissus Vivants,' 1SG6, p. 22. CI TAP. XXVII. OF PANGENESIS. 369 has its proper life, its autonomy; it can develop and reproc1uce itself independently of the adjoining tissues. 'rhe great German authority, Virchow, 19 assert.s still more emphatically that each system, as the nervous or osseous system, or the blood, consists of an "enormous mass of minute centres of action ..... Every " element has its own special action, and even though it derive " its stimulus to activity from other parts, yet alone effects the " actual porformanee of its duties. . . .. Every single epithelial " and muscular fibre-cell leads a sort of parasitical existence " in relation to the rest of the body. . . . . Every single bone" corpuscle really possesses conditions of nutrition paculiar to "itself." Each element, as 1\Ir. Paget remarks, lives its appointed time, and then dies, and, after being cast off or absorbed, ~::3 replaced.20 I presume that no physiologist don~ts that, for mstance, each bone-corpusele of the finger differs from the corresponding corpuscle in the corresponding joint of the toe ; and there can hardly be a doubt that even those on the corresponding sides of the body differ, though almost identical in nature. This near approach to identity is curiously shown in many diseases in which the same exact points on the right and l~ft sides of t.he body are similarly affected; thus Mr. Paget 2 t gtves a drawmg of a diseased pelvis, in which the bone has grown into a most complicated pattern, but "there is not one " spot or line on one side which is not represented, as exactly as " it would be in a mirror, on the other." Many facts support this view of the independent life of each minute element of the body. Virchow insists that a single bonecorpuscle or a single cell in the skin may become diseased. The spur ~f a cock, after being inserted into the eye of an ox, lived for e1ght years, and acquired a weight of 306 grammes, or ~early fourt~en ounc~s.22 The tail of a pig has been grafted mt? t~~e. mrddle of ~ts back, a~d reacquired sensibility. D1•• Olher mserted a p1ece of penosteum from the bone of a young dog under the skin of a rabbit, and true bone was developed. A multitude of similar facts could be given The 19 ' Cellular Pathology,' translat. by 2Z :M:antegazza, quoted in 'Popular Dr. Co~lm c:e, 1860, pp. 14, 18, 83, 460. Science Review,' July 1865, p. 522. ~0 Paget, 'Surgical Patholo"v ' vol i ~a ' De l~t Production Artificielle des J 853, pp. 12-14. o.' .. , Os · p 8 ' 0 • ~ 1 Idem, p. 1 9. VOL. II. 2 ll |
