418 
terminations of branches still growing are, in pointed extremi- 
ties, carried forwards as growth proceeds, necessarily imply- 
ing (were this so) an interstitial mode of growth ; hut having 
since made an arrangement by which branches may be 
microscopically observed whilst in process of growth, he must 
now correct that statement. A growing branch has already 
its full diameter, but as it elongates, and the power of growth 
becomes enfeebled, it gradually narrows, and when the 
needle-like point is formed there is no more elongation. The 
extremity of a growing branch, as seen under the microscope, 
appears enveloped by a slight cloudiness in the liquid, which 
is gradually lifted up so as to precede the growing point ; 
and the continuous elongation of the branch presents a very 
curious appearance. The branches are delicate tubes, having 
thin, semi-transparent walls ; they collapse and fall in pieces 
when taken out of their native fluid. Under a high power 
of the microscope they present a finely granular structure, 
but not any trace of crystalline form. Both the silica of the 
solution, and the constituents of the crystal on which they 
grow, enter into their formation. The nature of the force 
which determines the assumption of a dendroidal form, and 
a tubular structure by these confessedly mineral formations, 
and their upright growth in opposition to the tendencies of 
gravitation, is neither simple aggregation nor crystallization. 
It presents certainly a remarkable resemblance to that by 
which is effected the grow'th of living tissues, under the 
influence of vitality, upon which it may serve to throw some 
light. And, so far, these structures seem to form one slight 
gap (amongst others) in that wall of demarcation by which 
it has generally been held that the inorganic mineral world 
is absolutely divided from the world of organization ; but 
here, manifestly, there is no attribute of vitality. In connec- 
tion with his subject, and as bearing on it, Dr. Heaton also 
noticed a communication by Mr. W. C. Roberts to the journal 
of the ‘ Chemical Society ’ of last year, upon the occurrence 
of organic forms in colloid silica as obtained by Graham’s 
process of dialysis. These specimens have all the appearance 
of microscopic fungi, presenting radiating fibres composed of 
elongated cells, and bearing fructification, having much 
resemblance to some common forms of mildew. 
Report on the Examination of Animal Substances with 
the Spectroscope. By E. Ray Lankester. — The report first 
dealt with the methods of using the spectroscope in ob- 
serving absorption spectra. A spectrum map of N 2 0 4 gas, 
containing nearly forty numbered lines, had been printed and 
used by the reporter for recording spectra. The report then 
