In the first instance, no doubt, the names of the zodiacal constellations would depend on the principal star or stars in each, and these stars and the portion of the ecliptic assigned to each may have been noticed before the stars round them were grouped into constellations with different names. In any case, the introduction of the zodiac into Greece seems to have been subsequent to that of the celestial sphere, and not to have taken place more than five or six centuries before our era. Eudemus, of Rhodes, one of the most distinguished of the pupils of Aristotle, and author of a History of Astronomy, attributes the introduction of the zodiac to Oenopides of Chio, a contemporary of Anaxagoras. They did not receive it complete, as at first it had only eleven constellations, one of them, the Scorpion, being afterwards divided, to complete the necessary number. Their zodiacal divisions too would have been more regular had they derived them directly from the East, and would not have stretched in some instances over 36 deg. to 48 deg., like the Lion, the Bull, the Fishes, or the Virgin--while the Crab, the Ram, and the He-Goat, have only 19 deg. to 23 deg.. Nor would their constellations be disposed so irregularly, some to the north and some to the south of the ecliptic, nor some spreading out widely and others crammed close together, so that we see that they only borrowed the idea from the Easterns, and filled it out with their ancient constellations. Such is the opinion of Humboldt. With regard to the origin of the names of the signs of the zodiac, we must remember that a certain portion of the zodiacal circle, and not any definite group of stars, forms each sign, and that the constellations may have been formed separately, and have received independent names, though afterwards receiving those of the sign in which they were. The only rational suggestion for the origin of the names is that they were connected with some events which took place, or some character of the sun's motion observed, when it was in each sign. Thus we have seen that the Balance may refer to equal nights and days (though only introduced among the _Greeks_ in the time of Hipparchus), and the Crab to the retrogression or stopping of the sun at the solstice.