184 
NOTICES OF SCIENTIFIC MEMOIRS 
It is of special interest that all of these nebulae lie in the Magellanic 
Clouds, and that they are the only nebulae thus far observed by us in 
the Clouds. The first object, N. G. C. 1644, is in the Smaller Cloud, and 
the other four are in the Greater Cloud. 
It is difficult to doubt that these nebulae are actually within the struc- 
ture of the two Clouds, respectively: N. G. C. 1644, seen upon the Smal- 
ler Magellanic Cloud as a background, is the only known bright-line 
nebula in that region of the sky;^ and the others are four of the nineteen 
known bright-Hne nebulae closely clustered upon the background of the 
Greater Magellanic Cloud, which are almost equally isolated from other 
nebulae of their kind. 
Again, the radial velocities of the four nebulae observed in the Greater 
Cloud lie between 250 and 300 km. per second, recession. We should 
not expect the substantial equality of such high velocities unless the 
four objects bear a close relationship to each other or to the structure 
of the Greater Magellanic Cloud as a whole. It seems desirable that 
an effort should be made to measure the radial velocities of as many of 
the faint stars in the Magellanic Clouds as time and means will permit, 
in order to determine whether the average velocities of the stars in the 
Clouds approximate the velocities of the nebulae existing in the Clouds; 
that is, to determine whether the Magellanic Clouds possess high veloci- 
ties of recession with reference to our general stellar system. 
One is also inclined to inquire whether a more or less intimate resembl- 
ance may exist between the characters of the Magellanic Clouds and of 
the spiral nebulae, inasmuch as the spirals have been observed by 
Slipher to possess abnormally high radial velocities. 
1 For list of nebulae known to have bright-line spectra, see Annals of Harvard College 
Obs.,76,21 (1914). 
NOTICES OF SCIENTIFIC MEMOIRS 
Monograph of the Bomhycine Moths of North America, including their Trans- 
formations and Origin of the Larval Markings and Armature. Part III. 
Families ceratocampidae {exclusive of ceratocampinae) , saturniidae, hem- 
leucidae, and hrahmaeidae. By Alpheus Spring Packard, edited by 
Theodore D. A. Cockerell. First Memoir of Volume 12 of the Memoirs 
of the National Academy of Sciences. Washington, 1914. 1-502 p. 34 
fig. 113 pi. 
The third part of the late Dr. A. S. Packard's Monograph of the Bomhycine 
Moths of North America, published on December 31, 1914, by the National 
Academy of Sciences, and containing 16 pages including 34 figures and 113 
