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evidence, however, can be led tO contradict the answer in the latter case, unless it refer to a preVious conViction, or to circumstances tending to. throw doubt on the impar- tiality of the witness. A witness may 1n cross—examina- tion, and a witness proving hostile or adverse to the party calling him, may, in examination-in—chief, be asked whether he had not on a former occasion made statements inconsistent with his present statements. The credit Of a witness may also be impeached by the other party calling witnesses to swear that they believe him to be unworthy of belief, and counter-evidence may be given in reply. The

questions are improper if the imputation would not affect, or.would affect in a slight degree, the Opinion Of the court as to the credibility Of the witness on the matter to which he testifies; (3) Such questions are improper if there is a great disproportion between the importance Of the imputation made against the witness’s character and the importance of his evidence."

EVO—EVO

theory of the proceedings is that a Witness will tell his story in the most favourable way for the party calling him and against his opponent.

The improper admission or rejection of evidence was formerly a frequent ground for applications for new trial; under the Judicature Act a new trial will only be granted on such ground when some substantial wrong has been occasioned thereby.

The following are the most important writers on the law of evidence :—J Olin Pitt Taylor (two vols. 8v0, 6th edition, London, 1872); Henry Roscoe (Digest of the Law of Eridence on the trial of actions at NisiPrius,l3th edition, by Dayand l’owell, London, 1875); A. M. Best (0n the Principles of the Law of Evidence, with clemen- tary rules for the interrogation of witnesses, 6th edition, London, 1875); Edmund Powell (Principles and Practice of the Law ofEt-i- dance, 4th edition, London, 1875); Sir J. 1“. Stephen (Digest of the Law of Evidence, London, 1877); S. GreenleuHUlt the Law of Evi- dence, 3 vols. 13th edition, Boston, 1876). (E. It.)

EVOLUTION

I. EVOLUTION IN BIOLOGY.

N the former half of the 18th century, the term “evolu- tion” was introduced into biological writings, in order to denote the mode in which some of the most eminent physiologists Of that time conceived that the generation of living things took place; in Opposition to the hypothes1s advocated, in the preceding century, by Harvey in that remarkable work1 which would give him a claim to rank among the founders of biological science, even had he not

been the discoverer of the circulation of the blood.

One of Harvey’s prime objects is to defend and establish, on the basis of direct observation, the opinion already held by Aristotle; that, in the higher animals at any rate, the formation of the new organism by the process Of gene- ration takes place, not suddenly, by simultaneous accretion of rudiments of all or the most important of the organs of the adult; nor by sudden metamorphosis of a forma- tive substance into a miniature of the whole, which subse- quently grows; but by epigenesis, or successive differentia- tion of a relatively homogeneous rudiment into the parts and structures which are characteristic of the adult.

“ _Et prime, quidem, quoniam per epigenesin sive partium super- exorientium. additamentnm pulluin fabricari eertum est: quzenam pars ante alias omnes exstruatur, et quid de illa ejusque generandi mode Observandum veniat, dispiciemus. Ratuni sane est et in ovo manifeste apparet guodAristoteles de perfectorum animaliuin genera- tione enuntiat: nimi_ruin, non omnes partes simul fieri, Sed ordine aham post aham; primiimque existere particulain genitalein, cujus Virtute postea (tanquain ex principio quodam) reliqum Oinnes partes prosfliant. Qualein in plantarum seminibus (fabis, puth, aut glandibus) gel-111113.111 Sive apieem pi'otuheranteni ceniimus, totius futurm arboris prinCipium. Estque hcec particula velutfilius eman- cipatus seorsamque collocatus, ct principium per se cit-ens; mule postca meinhroi'urn 'ordo describitur; et quoecunque ad absolveiuium animal pertinent, disponuntur.2 Quoniam enim nulla pars se ipsam generat; seat posiquam generata est, se ipsam jam augct ,- idco cam primum orzri necesse. est, quoe principium augendi contineat (sine emm planta, swe animal est, oeque omnibus incst quod rvim habeat vegetandi, sine natriendi),3 simulque reliquas omnes partes suo quapique ordine distinguat et formet; prOindeque in eadem primo- gcnita particula amina primariO inest, sensus, motusque, et totius Vitae auetor et princ1piuni." (Exercitatio 51.)

“ Harvey, proceeds to contrast this view with that of the “h[edlCl,' _or followers of Hippocrates and Galen, who,

badly pnilosophizing,” imagined that the brain, the heart, and the liver were simultaneously first generated in the form of vesicles: and. at the same time, while expressing his agreement With Aristotle in the principle Of epigenesis, he maintains that it is the blood which is the primal genera- tive part, and not, as Aristotle thought, the heart.

1 The Exercitatione de Generatione A ‘ ' ' . s. mmalzum which Dr 0 Enzt extracted from him and published in 1651. ’ Ge rgc 8 De Generationc Animalium, lib. ii. cap. x. Dc Generatione, lib. ii. cap. iv.

In the latter part of the 17th century, the doctrine of epigenesis thus advocated by Harvey was controverted on the ground of direct observation by Malpighi, who affirmed that the body Of the chick is tO be seen in the egg before the punctum sanguinesz makes its appearance. But from this perfectly correct observation a conclusion which is by no means warranted was drawn 3 namely, that the chick as a whole really exists in the egg antecedently to incubation; and that what happens in the course Of the latter process is no addition Of new parts, “alias post alias natas,” as Harvey puts it, but a simple expansion or unfolding of the organs which already exist, though they are too small and inconspicuous to be discovered. The weight of Malpighi’s Observations therefore fell into the scale Of that doctrine which Harvey terins metamorphosis, in contradistinction to epigenesis.

The views of Malpighi were warmly welcomed on philo- sophical grounds by Leibnitz,4 who found in them a support to his hypothesis Of monads, and by Malebranche;5 while, in the middle of the ]8th century, not only specula- tive considerations, but a great number of new and interest- ing Observations on the phenomena Of generation, led the ingenious Bonnet, and Haller,6 the first physiologist of the age, to adopt, advocate, and extend them.

Bonnet affirms that, before fecundation, the lions egg

‘ “ Cependant, pour revenir aux formes ordinaires ou aux ames matérielles, cette durée qu'il leur faut attribuer, a la place de celle qu'on avoit attribuc’e aux atomes pourroit faire douter si elles ne vont pas de corps en corps; ce qui seroit la métempsychose, a pen pres comme quelques philosophes out cru la transmission (In iuouvement et celle des espéces. Mais cette imagination est bien eloignée de la nature des choses. ll n’y a point de tel passage; et c'est ici Oii les transfor- mations de Messieurs Swammerdam, Malpighi, et Leewenhoek, qui sont (les plus excellens observatenrs de notre teins, sont venues a men secours, et m’ont fait adinettre plus aisement, que l'animal, et toute autre substance organisée ne commence point lorsque nous 1e croyons, et que sa generation apparente n'est qu’une développement et une espece d’augmentation. Aussi ai je remarque’ que l’auteur de la Recherche tie la Verité, M. Regis, M. Hartsoeker, et d’autics habiles hommes n'ont pas été fort éloignés de ce sentiment.” Leibnitz, Sys~ téme none-can de la Nature, 1695. The doctrine of “ Einhoiteinent ” is contained in the Considerations snr le principerle Tie, 1705; the preface to the Thendice’e, 1710; and the Principes de la Nature ct de la Grace (§ 6), 1718.

5 “Il est vrai que la pensée la plus raisonnable et la plus conforme ii. l'experience sur cette question trés difficile de la formation du foetus; c'est que les enfans sont déja presque tout form'es avant ménie l'action par laquelle ils sont concus; et que leurs meres ne font que leur dormer l'accroissement ordinaire dans le temps do 13 grossesse.” De la. Recherche de'la Verité, livre ii. chap. vii. p. 334, 7th ed, 1721.

6 The writer is indebted to Dr Allen Thomson for reference to the evidence contained in a note to IIaller’s edition of Boerhaave's I’rtelec- tiones Academica’, vol. v. pt. ii. p. 497, published in 1744, that Ilaller originally advocated epigenesis.