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ASTRONOMY: F. H. SEARES 217 The only plus value comes between the first two periods and the lowest values are between the 8-10 and the 10-12k day periods. An examination of these values and a comparison with the facts of histogenesis shows that acceleration of rate is a plus quantity only during the period before active differentiation of the cells has begun. The retarding effect is evident with the beginning of apparent tissue differentiation and by the ninth to eleventh days the negative acceleration is at its height. The percentage increments for the six periods represented are respectively 106, 28, 12, 5, 0 and 0 (fig. 5). There is a very rapid decrease at first and then a slower and slower one as zero is approached. The data agree with those of ordinary growth. First regenerations of frog tadpoles gave results which were essentially similar to those for second regenerations. The data will appear in full in the University of Illinois Biological Monographs. PRELIMINARY NOTE ON THE DISTRIBUTION OF STARS WITH RESPECT TO THE GALACTIC PLANE By Frederick H. Seares MOUNT WILSON SOLAR OBSERVATORY. CARNEGIE INSTITUTION OF WASHINGTON Commuicated by G. S. HaleI February 9.1917 significant feature of the distribution of stars over the face of the is sky their concentration toward the plane of the Galaxy. Approaching the Milky Way from either side, we find that objects of all degrees of brightness become more and more numerous; with decreasing galactic latitude, the star-density regularly increases and attains a maximum in the star clouds of the Milky Way itself, a fact long known and, as early as 1750, the basis of cosmological speculation by Thomas Wright of Durham.1 The phenomenon was studied by both the Herschels, and more recently Seeliger, Celoria, Pickering, Kapteyn,2 and Chapman and Melotte,8 among others, have given values of the stellar density; and ye