That such latter-day appropriation is the fact is clearly hinted by the behavior of another understudy of an original canal, in this case the duplicate of the Djihoun, which in consequence of the position of its original finds no neighboring embouchure already convenient to its use. The single or original Djihoun leaves the tip of the needle-pointed Margaritifer Sinus, which serves a like end to the Oxus and the Indus, both single canals. The Sinus is itself a single bay, and so large that for many degrees its shores on both sides converge smoothly to their sharp apex. Because of this probably, the coast in the immediate neighborhood is without canal connection, no canal being known along either side till one reaches the Hydraotes at the Aromaticum Promontorium, which marks the western limit of the gulf. The consequence is that when the Djihoun doubles, the duplicate canal, not having any terminus ready to its hand, has to make one for itself by simply running into the Margaritifer Sinus, some distance up its eastern side. It thus advertises its adjunctival character, and at the same time the general fact that a neighbor’s terminus, though used from preference, when convenient, is not an essential in the process. Gemination occurs of its own initiative, but is conditioned by convenience. Whether one canal shows thus to the exclusion of the other, or whether both stand so confused as not to be told apart, the fact remains that the double is not always recognizable as such. If we turn to the list of the doubles on page 222, we shall note that the same canals were not always seen in the dual condition at successive oppositions. Some, indeed, are so emphatically of the habit as to appear year after year in a paired state, but others are not so constant to their possibilities. Now, when it is remembered that at different oppositions we view Mars at diverse seasons of its tropical year, we see that this means that the phenomenon is seasonal; and furthermore that its exhibition depends upon the canal’s position. Gemination, like the showing or non-showing of the single canal, is conditioned by the place of the canal upon the planet. III