In endeavouring to trace the causation of adaptation, it is obvious that it must be due quite as much to properties inherent in the plant as to the action of external conditions; the plant must possess adaptive capacity.
The prince, after vainly endeavouring to obtain the recall of the generals, restored the constitution with the concurrence of all the Bulgarian political parties (September 18, 1883).
The indigenous inhabitants; and the rapid succession of conquerors, Lombards, Franks and Germans following each other at no long interval, and each endeavouring to weaken the remaining strength of his predecessor, prevented this alien hierarchy from acquiring ixity by permanence of tenure.
Though severely tried by disappointments and defeats he never lost hope, and when he died in 1584 he was preparing to renew the struggle and endeavouring to form for that purpose an alliance with England; his great idea, however, was not to be realized till more than a century later, and meanwhile the tsardom of Muscovy had to pass through a severe internal crisis in which its existence was seriously endangered.
That conviction he put into practice with extreme rigour during the thirty years of his reign (1825-55), endeavouring by every means at his disposal to prevent revolutionary ideas from germinating spontaneously among his subjects and from being imported from abroad.