ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 245 



sible to doubt that when the vegetable cell dissolves its own starch, 

 some must needs pass out by osmosis into the closely enveloping pro- 

 toplasm of the surrounding animal cell, which possesses abundance of 

 amylolytic ferment. Further, the nutritive functions of the animal 

 gain by digesting the Philozoon at its death. On the other hand, the 

 carbonic acid and nitrogenous waste produced by the animal cell are 

 necessities of life to the alga, which in removing them performs an 

 intracellular renal function. Yet further, during sunlight the alga 

 constantly evolves nascent oxygen into the surrounding animal proto- 

 plasm, and so we have foreign vegetable chlorophyll performing the 

 respiratory functions of native animal haemoglobin, and the resem- 

 blance becomes closer when we bear in mind that hsDmoglobin fre- 

 quently lies as a stationary deposit in some tissues like the tongue of 

 certain molluscs and the nerve-cord of Aphrodite and Nemerteans. 



Thus, then, " for a vegetable cell no more ideal existence can be 

 imagined than that within the body of an animal cell of sufficient 

 active vitality to manure it with abundance of carbonic anhydride and 

 nitrogenous waste, yet of sufficient transparency to allow the free 

 entrance of the necessary light. And conversely for an animal cell 

 there can be no more ideal existence than to contain a sufficient 

 number of vegetable cells, constantly removing its waste products, 

 supplying it with starch and oxygen, and being digestible after 

 death. ... In short, we have here economic inter-relations of 

 the animal and the vegetable world reduced to the simplest and closest 

 conceivable form." 



That this is no mere case of parasitism is further proved by the 

 fact that it is exactly those animals containing the algae (" animal 

 lichens," as the author suggests they might not unfairly be called) 

 which show exceptional success in the struggle for existence, instead 

 of the weakened state to be found in the host of a parasite. They are 

 not only far more abundant, but are capable of enduring greater hard- 

 ships than their less fortunate allies. 



Mr. G. Murray * considers that " to botanists these investigations 

 bear a very peculiar interest. No nearer analogue to this ' censor tism,' 

 if it may be called so, of the animal and the vegetable (algal) cell can 

 be found than in that of the fungal and algal cells of the lichens. It is 

 so apparent throughout that it is needless to enter into a detailed com- 

 parison. One point in the analogy, however, is noteworthy. The 

 young gonophores of Velella which bud off from the parent colony, 

 start in life with a provision of Philozoon. One cannot but be forcibly 

 reminded by this of the function of the hymenial-gonidia of such 

 lichens as Dermatocarpon, Polyblastia, &c., as described by Professor 

 Stahl. The hymenial-gonidia, which are the offspring of the thallus- 

 gonidia, are carried up in the formation of the apothecia, and are cast 

 out along with the spores. Falling in the same neighbourhood, the 

 spores, on germinating, enclose with their filaments the hymenial- 

 gonidia, which ultimately become the thallus-gonidia of the new 

 lichen. The fact that among these animals the most closely allied to 

 each other morphologically differ thus widely physiologically, bears 

 * ' Academy,' No. 508 (1882) p. 67. 



