Astronomy. 131 
tean forms certainly show that the plan, upon which the Echinoderms 
are built, does not differ from that upon which the Acalephs are built, 
and that we have between the Echinoderms and Acalephs the same con- 
shown, by Prof. Agassiz, to exist in the adult of many Echinoderms, 
while the facts above stated prove that it also exists in the early stages 
the embryonic development, when, in fact, the water-system is ormed 
appears 
the inclinations I of the planetary orbits toward the invariable plane 
“ . 
Ments seem n 
Let ¢ be the inclination of the orbit, and 7’ the inclination of the inva- 
riable plane toward the ecliptic. As the values of z themselves are 
subject to quite considerable changes, we deemed it unnecessary to cal- 
culate the exact values of I, and made use of the equation 
ee I a a’ - +; 
i.e. subtracting the smaller from the greater angle. 
+ Th the editor has induced us to calculate the exact values of 
I in order to see how great an e i mitted in neglecting the 
erical excess A of the spherical triangle. From the fifth edition of — 
‘commana Astronomie Populaire (Berlin, 1861) we take the following 
” elements : = 
Q i 
Mercury, 46° 23’ 55” v" ia 
Venus, 75 1k 29°8 3 23 31 °4 
Mars, 48 16 18-0 1 61 67 
Jupiter, 98 48 37-8 1 18 42 4 
Saturn, ee oe ey ae 2 29 29 9 
Uranus, 43 8 47:8 46 29 -2 
Neptun 129 5 
Tuvariable plane, 106 © 49 ‘0 
