POPULAR MISCELLANY. 



285 



which the following conclusions were drawn : 

 1. The combined nitrogen, which is the 

 product of vegetable and organic life, forms 

 the chief source of nitrogen for the grow- 

 ing plant. 2. Before it is assimilated by the 

 plant, it undergoes a process of oxidation 

 which is due solely to a living organism. 

 3. The nitrates thus formed are absorbed by 

 the plant, and the albuminoids of the new 

 growth are formed from the nitric nitrogen 

 by a process of reduction. The nitrates 

 themselves are subject to the action of a 

 ferment by which a deoxidation takes place, 

 and free nitrogen and nitrous oxide are 

 evolved. 4. The diminution in the quan- 

 tity of available nitrogen thus supplied is 

 restored by the fixation of free nitrogen, by 

 the action of organisms in the soil, or by the 

 oxidation of free nitrogen by the interior 

 cells of the plant acting in a manner analo- 

 gous to the nitric ferment in the soil, or by 

 the oxidation of free nitrogen by electrical 

 discharges or by combustion. 5. The quan- 

 tity of combined nitrogen brought to the 

 seil and growing plant by the rain-water 

 and the atmosphere, arising from the last 

 two phenomena, is an inconsiderable amount 

 when compared with the whole weight re- 

 quired by the crop. Concerning the future 

 food-supply, Professor Wiley said : " Siuce, 

 with a proper economy, the natural supplies 

 of potash and phosphoric acid may be made 

 to do duty over and over again, and last in- 

 definitely, the economist, who looks to the 

 welfare of the future, need have no fear of 

 the failure of these resources of the grow- 

 ing plant. Indeed, it may be said that the 

 available quantities of these may be in- 

 creased by a wide practice of agriculture 

 based on the teachings of agricultural chem- 

 istry. But with the increase of population 

 comes an increased demand for food, and 

 therefore the stores of available nitrogen 

 must be enlarged to supply the demands 

 of the increased agricultural product. It is 

 certain that with the new analytical meth- 

 ods, and the question raised by the investi- 

 gation-, many scries of experiments will be 

 undertaken, the outcome of which will defi- 

 nitely settle the question of the entrance 

 of free nitrogen into vegetable tissues. If 

 this question be answered affirmatively, ag- 

 ricultural science will not place bounds to 

 the possible production of foods. If the 



nitrifying process goes on within the cell3 

 of plants, and if living organisms do fix 

 free nitrogen on the soil in a form in which 

 at least a portion of it may be nitrified, we 

 may look to sec the quantities of combined 

 nitrogen increased pari passu with the needs 

 of plant-life. Thus, even intensive culture 

 may leave the gardens and spread over the 

 fields, and the quantities of food suitable 

 for the sustenance of the human race be 

 enormously increased." 



Evolution of Means of Defense. — Mr. 



Charles Morris, in a paper of the Academy 

 of Natural Sciences of Philadelphia, on 

 " Attack and Defense as Agents in Evolu- 

 tion," suggests that the various modifica- 

 tions which are seen in the hard parts of 

 animals at different periods indicate adap- 

 tation to dominant ideas that have different 

 relations to the prevailing conditions of ex- 

 istence of the time. The earliest animals 

 were probably wholly soft, and have left no 

 remains except an occasional track on the 

 mud of their day. Then came in armored 

 forms with external shells. Swift-swimming 

 armored animals came in with the fishes, 

 and seem to have increased in thickness 

 and weight of armor to the end of the De- 

 vonian era. " If, now, we come down to a 

 later era of life, we find in operation what 

 seems a third idea of Nature. The prevail- 

 ing tendency in animal life is no longer to 

 assume armor, but to throw off armor, and 

 return toward the unprotected condition. 

 The causes of these changes are related to 

 the development of weapons of assault in 

 attacking animals, and to the kind of de- 

 fense that was most available and useful, 

 or most efficient at the period. As Mr. 

 Morris says : " In the primeval epoch it is 

 probable that only soft-bodied animals ex- 

 isted, and the weapons of assault were the 

 tentacles, the thread-cell, the sucking-disk, 

 and the like unindurated weapons. At a 

 later period armor became generally adapt- 

 ed for defense, and the tooth became the 

 most efficient weapon of attack. Still later, 

 armor was discarded, and flight or conceal- 

 ment became the main method of escape, 

 and swift pursuit the principle of attack, 

 while claws were added to teeth as assail- 

 ing weapons. Finally, mentality came into 

 play, intelligence became the most efficient 



