This arrangement was by no means final. Further changes were made in both foot and horse which were to have a bearing on the organization of the comitia centuriata. After a time[448] two additions of men less heavily armed than the classici were made to the phalanx, whether simultaneously or successively cannot be determined. There were now forty centuries of classici, and the additions comprised ten centuries each, the second less heavily armed than the first, though they may both be considered heavy in contrast with the light troops. Perhaps the state according to its ability made up the deficiency in the equipment, so as to render the entire phalanx as evenly armed as possible.[449] It numbered sixty centuries of heavy infantry, composed of three grades which depended upon the census rating.[450] The light troops were also grouped in two divisions on the same principle. The first comprised ten centuries; originally the second may have contained the same number, in which case four were afterward added to make the fourteen known to exist in the fully developed system.[451] There were five divisions of infantry amounting to eighty-four centuries of a hundred men each. Undoubtedly the growth of the army to this degree of strength was gradual, though the successive steps cannot be more minutely traced.[452] In making the levy the military tribunes selected the soldiers from the lists of tribesmen, taking one tribe after another as the lot determined.[453] The early Romans must have striven to distribute the population as equally as possible among the tribes in order to render them approximately equal in capacity for military service. As long as this equality continued, the officials could constitute the army of an equal number of men from each tribe. These considerations explain the close relation in early time between the number of tribes and of centuries as well as the suggestions offered by our sources as to an early connection between the centuries and the tribes.[454] While there were but twenty tribes we may suppose that the legion comprised but 4000 men, which was raised to 4200 when the twenty-first tribe was added. In this way can we account for the number of centuries to the legion. If but half the available military strength was required, the magistrates might draw by lot ten tribes from which to make the levy.[455] It was an easy matter as long as the heavy troops were limited to the classis;[456] but when two other ratings were added, and when meantime the tribes must have grown unlike in population, it became practically impossible to maintain for each rating a just proportion from the tribes;[457] and perhaps this was the chief reason for the modification in the method of recruiting. When therefore the tribes were increased to twenty-five, and it was deemed inexpedient to make a corresponding enlargement of the legion,[458] a new principle was adopted for the levy: after determining