174 Transactions of tlie [Sess. 



essential in the hivmoglobin of blood, as well as in the chloropby]] 

 of plants, being a remarkable point of affinity between these very 

 important and very active organic products. 



(5) Most animals possess a distinct alimentary tract, which, al- 

 though not found as a definite elongated digestive tube in vegetables, 

 is still represented by the pitchers of Sarracenia, Darlingtonia, and 

 Nepenthes. These perform all the functions of a stomach, being 

 specially constructed for the capture and digestion of insects, as cock- 

 roaches, &c. ; while the glands found in them function in the same 

 way as the gastric glands of the most highly developed mammalian 

 stomach, by secreting a vegetable gastric juice. Moreover, these 

 pitchers are epidermic involutions of leaves, just as the primitive 

 archenteron of an animal gastrula is in many cases an invagination of 

 an original epiblastic wall of cells. 



(G) All plants except the Fungi and a few highly organised yet 

 parasitic Phanerogams, such as Lathrtea, possess green colouring 

 matter or chlorophyll, the function of which is the decomposition of 

 carbonic acid (COj) in sunlight, and the fixation of carbon with 

 liberation of oxygen, so that organic matter, such as starch, is formed 

 by plant agency out of such simple inorganic bodies as carbonic 

 acid and water ; while even Fungi like Penicillium can form organic 

 constituents " out of ammonium tartrate, sulphate, and phosphate 

 dissolved in water," although these Fungi may in most cases directly 

 assimilate proteinaceous substances contained in the bodies of the 

 plants or animals which they attack, — the Saprolegnia of Salmon 

 disease removing the rich albuminous products of its host, no less 

 than the Peronospora of Potato blight. 



Animals, on the other hand, are, for the most part, incapable of 

 elaborating organic compounds out of tlieir simple inorganic com- 

 ponents, in virtue of an absence of chlorophyll, so that we have 

 here to deal with a reciprocal action between the two organic king- 

 doms. Yet the existence of green animals is well known ; and 

 the list of Alga-bearing animals, as given by Professor Lankester 

 and Dr Karl Brandt, includes organisms of very diiFerent grades — 

 Infusoria, Foraminifera, Eadiolaria, Coelenterata, Ctenophora, Vermes, 

 Crustacea, Mollusca, Bryozoa, and Echinodermata. It is to be re- 

 marked, however, that greenness in animals need not be due to the 

 existence of chlorophyll as such. There would seem, indeed, to be 

 other green pigments developed chiefly for protection,^ and not of 

 the same physiological significance as chlorophyll, — pigments which 

 have sometimes received special names, according to the animal in 

 which they have been found. Thus we have the Bonellein of 



^ In the same way Grasshoppers (Acridiidse) tend to be protected by their 

 colour; and the orthopterous Phasmida — the "walking-leaf" and "stick" 

 insects — curiously mimic leaves and pieces of branches. Of such protective 

 resemblances there are many illustrations in organic nature. 



