472 Royal Society. 



argues on several grounds that they have no true affinity with the 

 gastric teeth of the Crustacea, though he states his conviction 

 that the Rotifera belong to the great Arthropodous division of 

 animals. 



It is with the Insecta that the author seeks to ally these minute 

 creatures ; and, by a course of argument founded on the peculiarities 

 of structure already detailed, he maintains the following identifica- 

 tions : — that the mastax is a true mouth ; that the mallei are mandi- 

 bles ; the manubria possibly representing the cheeks, into which they 

 are articulated ; that the rami of the incus are maxilla ; and that the 

 fulcrum represents the cardines soldered together. 



While the author maintains the connexion of Rotifera with 

 Insecta, through these organs in their highest development, he 

 suggests their affinity with Poiyzoa, by the same organs at the 

 opposite extremity of the scale, since the oval muscular bulbs in 

 Boiverbankia, which approach and recede in their action on food, 

 seem to represent the quadriglobular masses of Limnias and Rotifer, 

 further degenerated. 



If this affinity be correctly indicated, the interesting fact is appa- 

 rent, that the Poiyzoa present the point where the two great parallel 

 divisions, Mollusca and Articulata, unite in their course towards 

 the true Polypi. 



March 8, 1855.— Sir Benjamin Brodie, Bart., V.P., in the Chair. 



The following paper was read : — 



" On the Perihelia and Nodes of the Planets." By Edward J. 

 Cooper, F.R.S. 



Prefatory to my volume on Cometic Orbits, published in 1852, I 

 invited the attention of astronomers to the several points of resem- 

 blance between the planetary orbits and those of periodic comets. 

 Among these it was shown, that of the heliocentric longitudes of 

 perihelia and ascending nodes of the then known planets and periodic 

 comets, two-thirds were situated in the heliocentric semicircle 

 between 315° and 135°. The planets stood thus in quadrants — 



L. P.'s between 45 and 135 = 



135 and 225 =< 



225 and 31 



315 and 45 = 

 $, between 45 and 135 = 



135 and 225=' 



225 and 31 



315 and 45 = 



Here the L. P.'s appeared as 16 to 7, and the ascending nodes as 

 14 to 8. Two additional asteroids were subsequently discovered 

 leaving the L. P.'s as 16 to 9, and the ascending nodes as 15 to 9. 

 Again, in 1853, I sent a note upon the same subject to the Royal 

 Astronomical Society of London. At that time a considerable addi- 

 tion had been made to the asteroids, and the total number of planets 

 had risen from 25 to 35. Following the same distribution of the 



