'Royal Institution. 409 



It is not mere external form which constitutes Organization. On 

 the table there was a lead-tree (as it is called), which, a mere product 

 of crystallization, possessed the complicated and graceful form of a 

 delicate Fern. If a section, however, were made of one of the leaflets 

 of this "tree," it would be found to possess a structure optically and 

 chemically homogeneous throughout. 



Make a section of any young portion of a real plant, and the result 

 would be very different. It would be foimd to be neither chemically 

 nor optically homogeneous, but to be composed of small definite 

 masses containing abundance of nitrogen imbedded in a homogeneous 

 matrix having a very different chemical composition. The lecturer 

 explained that it would save a great deal of confusion if two new 

 terms were adopted — that of Endoplast for the imbedded masses 

 (Primordial utricle, nucleus, cotitents oi axxthors) ; that o? Periplastic 

 substance for the matrix {cell-wall, intercellular substance of authors). 

 In all young animal tissues the structure is essentially the same, con- 

 sisting of a homogeneous periplastic substance with imbedded endo- 

 plasts {nuclei of authors), as the lecturer illustrated by reference to 

 diagrams, and he therefore drew the conclusion that the common 

 structural character of living bodies as opposed to not living, is 

 the existence in the former of a local physico-chemical differentia- 

 tion ; while the latter are physically and chemically homogeneous 

 throughout. 



These facts, in their general outlines, have been well known since 

 the promulgation in 1838 of the celebrated cell-theory of Schwann. 

 Admitting to the fullest extent the meritorious service which this 

 theory had done to physiology, the lecturer endeavoured to show 

 that it was infected by a fundamental error, which had introduced 

 confusion into all later attempts to compare the vegetable with the 

 animal tissues. This error arose from the circumstance that when 

 Schwann wrote, the primordial utricle in the Plant-cell was unknown. 

 Schwann therefore, who started from the structure of Cartilage, sup- 

 posed that the corpuscle of the cartilage cavity was homologous with 

 the " nucleus " of the vegetable cell, and that therefore all bodies in 

 animal tissues homologous with the cartilage corpuscleswere " nuclei." 

 This conclusion is a necessary result of the premisses ; and therefore, 

 the lecturer stated that he had carefully re-examined the structure 

 of Cartilage, in order to determine which of its elements corresponded 

 with the primordial utricle of the Plant, — the important missing 

 structure of which Schwann had given no account. 



The general result at which he had arrived was this : — In all the 

 animal tissues the so-called nucleus (Endoplast) is the homologue of 

 the primordial utricle (Endoplast) of the Plant, the other histological 

 elements being invariably modifications of the periplastic substance. 



Upon this view it becomes easy to trace the absolute identity of 

 plan in the organization of Plants and Animals, the differences between 

 the two being produced merely by the nature and form of the deposits 

 in or modifications of, the periplastic substance. 



Thus in the Plant, the endoplast of the young tissue becomes a 

 primordial utricle, in which a "nucleus" may or may not arise; it 

 Ann. S^ Mag. N. Hist. Ser. 3. Vol xi. ' 27 



