riNNEAJir SOCIETY OF LONDON. xlui 



supplies the means of verifying or correcting descriptions or delinea- 

 tions which have excited suspicion. Their great drawback is their 

 incompleteness, the impossibility of deriving from them all the data 

 required for the knowledge of a race or even of an individual. It is 

 owing to the frequency vrith which characters supplied by preserved 

 specimens, although of the most limited and unimportant nature, 

 have been treated as sufficient to establish affinities and other ge- 

 neral conclusions which have proved fallacious, that the outcry I 

 have alluded to has been raised against museums and herbaria by 

 those very theorists whose speculations would fall to the ground if 

 all the data suppHed by preserved specimens were removed from 

 their foundations. 



In respect of these deficiencies, as well as in the means of sup- 

 plying them, there is a great difference between zoological and 

 botanical museums. Generally speaking, zoological specimens show 

 external forms only, botanical specimens give the mean% of ascer- 

 taining internal structure * ; and as a rule the characters most pro- 

 minently or most frequently brought under the observer's notice 

 acquire in his eyes an undue importance. Hence it is that external 

 form was for so long almost exclusively relied upon for the classifi- 

 cation of animals, whilst the minutiae of internal structure were at 

 a comparatively early period taken account of by botanists ; and 

 pala3ontologists are stiU led to give absolute weight to the most un- 

 certain of all characters, outline and external markings of deciduous 

 organs. External form, however, is really of far greater importance 

 in animals than in plants ; the number, form, size, and proportions 

 of limbs, the shape and colour of excrescences, horns, beaks, feathers, 

 hairs, &c. in animals may be reckoned almost absolute in species 

 when compared with the same characters in the roots, branches, 

 and foliage and, to a certain extent, even in the flowers of plants. 

 In plants, local circumstances, food, meteorological conditions, &c., act 

 readily in modifying the individual and producing more or less per- 

 manent races of the lowest degree (varieties) ; whilst animals in 

 these respects are comparatively little affected, except through those 

 slow or occult i)rocesses by which the higher races, species or genera, 

 in all organisms are altered in successive ages or geological periods. 

 Even relative position of external parts, so constant in animals, is 

 less so in plants. Animals being thus definite in outline, and a very 



* By mter7ial structure is here meant the morphology of internal organs or 

 parts usually included in the comparative anatomy of animals, not the micro- 

 Bcopical structure of tissues, which is more especially designated as vegetable 

 anatomy. 



