104 
JOURNAL OF THE PLYMOUTH INSTITUTION. 
the outline of the blood circulation in the class, and illustrated the 
arrangement and structure of the breathing organs in the peleostii 
or bony fishes, in the elasmobranchii or cartilaginous fishes, in the 
marsipobranchii, in the ganoidei, in the amphioxus, and in the 
lepidosiren. 
COMETS. 
ABSTRACT OF PAPER BY DR. MERRIFIELB, F.R.A.S., F.M.S. 
(Read January 11th, 1877.) 
The lecturer treated of the superstition among the ignorant, the 
forms of orbits of planets, contrasted those of planets and comets, 
and explained the elements of comets. He showed how they are 
recognized on their reappearance, sustained LexelPs comet; and 
gave a description of comets — nucleus, coma, and tail. Proof of 
small masses of comets from the effects of Encke's and Biorson's 
was noted ; and concerning the material of which comets are 
formed, proofs from polariscope and spectroscope. Reference was 
made to the number of comets that come within the solar system ; 
and their connection with star showers ; reasons given for believing 
in an intra-Mercurial planet ; and the effects of a collision indicated. 
COLOUR IN NATURE, 
AND ITS RELATIONS TO PRACTICAL PICTORIAL ART. 
ABSTRACT OF MR. A. SHELLY's PAPER. 
(Read January 18th, 1877.) 
It treated of light, colour, inherent colours, mixture of colours in 
nature, contrast of colour, technical processes of art in relation to 
mixture of colours, colour as influenced by daylight and atmospheric 
changes, light direct, reflected and transmitted shadow, warm and 
cool colours, clouds, foliage, water, and technical processes of art 
in relation to the foregoing. 
