XXU •• PROCEEDINGS OF THE 



tested chiefly by internal structure, the latter depending on adaptive 

 characters influencing outward form. The whole work appears to 

 me to be a good illustration of the German peculiarities I have 

 above alluded to — a searching investigation of facts, systematic, 

 structural, and physiological, with a rather free play given to 

 imagination and some confusion of ideas. His pedigrees, although 

 more plausible than Strasburger's or Delpino's, are still conjectural 

 only, unsupported by geological evidences, of which there appears 

 to be none in Calcisponges * ; and if he is right in the necessity of 

 keeping up an artificial system where the characters indicating 

 natural affinities are too difficult or too vague (perhaps too ima- 

 ginary) for practical use, yet I see no advantage in working out in 

 detail two sets of genera and species, natural and artificial, with 

 distinct names according to the light in which they are considered. 

 I cannot see why the same object should be known to one naturalist 

 by the name of Olynthus jprimordialis and to another by that of 

 Ascetta primordialis. The general pedigree of the zoological king- 

 dom (vol. i. p. 465) in a true heraldic form is certainly a very bold 

 stroke; and the two pedigrees of Calcispongian genera (pp. 359 & 

 360), natural and artificial, quite pass my comprehension. 



The study of organogenesis, which may be said to have been first 

 established as a distinct branch of the science in France, has been 

 followed up among French naturalists by that of the development 

 and course of the vascular system in phaenogamous plants and the 

 higher Cryptogams. Casimir de Candolle, in his ' Theorie de la 

 Feuille ' and other papers, Trecul and Van Tieghem, in various memoirs 

 in the ' Annales des Sciences Waturelles,' the ' Comptes Eendus,' and 

 other publications, have materially contributed to correct our 

 theories of the outgrowth and arrest of development of the various 

 parts of the plant as connected with the difierent functions they are 

 called upon to fulfil in its general economy. But here, again, as is 

 usually the case where some error has been detected in an esta- 

 blished theory, the disposition has been to declare the whole theory 

 false. There is no doctrine better established, no one which has 

 been found more practically useful in the history of the life and 

 relations of plant-races as well as of individuals, than that of the 

 homology of appendicular organs as distinguished from the axis — a 

 doctrine originally sketched out by Linnaeus t, poetically conceived 



* " No fossil Calcisponge is as yet known" (Hackel, Kalkschw. i. p. 341). 



t See " Prolepsis Plantarum," in the Amoenitates Academicae, ed. Schreb. vi. 

 324, where Linnreus shows by a number of examples the homology of bud-scales, 

 leaves, bracts, calyxes, petals, stamens, and pistils. 



