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This irregularity then increases more and more, until at last it grows into 
well-marked convulsions. The convulsions manifest themselves in the form 
of extreme deviations from the rhythmical character of the normal contrac- 
tions, amounting, in fact, to nothing less than tonic spasms. It is further 
of importance to remark that the convulsions are very plainly of a paroxys- 
mal nature — prolonged periods of uninterrupted convulsions being every now 
and then relieved by shorter periods of repose, during which the Medusa 
remains perfectly motionless in a fully expanded form. C. capillatn will live 
for many hours when under the influence of strychnia, but eventually death 
supervenes. The animal dies in full diastole.” 
The Development of the Bird is thus summed up by Mr. A. S. Packard, 
Junr., in the u American Naturalist”: — 1. Partial segmentation of the yolk. 
2. The embryo develops much as in the bony fishes until the embryonal 
membranes appear. 3. Formation of an amnion. 4. After the alimentary 
canal is sketched out, the allantois buds out from it. 5. The avian features 
appear from the sixth to the tenth day. 6. The embryo leaves the egg in 
the form of the adult, and like the reptile, is at once active, feeding itself. 
How are the Chameleon's Changes of Colour produced? — A very interesting 
paper on this subject is that of the JEtev. S. Lockwood, in the “American 
Naturalist” for January 1876. He gives the following admirable illustra- 
tion of the changes of colour. He says : — Supposing through a sheet of 
block tin many thousands of little pipes were made just to enter. Let them, 
if you will, be regarded as infinitely small. Call this series A. Now suppose 
another series in all respects similar and fixed in like manner. Call this 
series B. It must be understood that the pipes of one series alternate with 
those of the. other series, so that it shall be first a pipe of A, then a pipe of 
B, and so on in regular order for both series. Suppose again that the A 
pipes contain green pigment, and the B pipes contain yellow. We will 
further imagine that each pipe series has a series of muscles which can act 
upon them. Now laid over the mouths of all these pigment tubes let us 
suppose a translucent film. Our perforated block tin and its translucent 
spread, with the mouths of the colour-tubes opening between them, shall 
represent the rete mucosum, or coloured layer of the skin. Suppose now the 
appropriate muscles squeeze the lower ends of the A series of pigment- tubes, 
the pigment at once comes up against the almost transparent skin, the 
colour of which is now blue. Let the muscles relax and the pigment 
descends into the tubes again. Let the same process occur with the B series 
of tubes, and the result will be that the skin shows a yellow colour. Not 
waiting for the yellow pigment to return into the tubes, let the A series be 
again squeezed, and up comes the blue pigment against the translucent 
spread. Now everybody knows that a green colour is easily made by a 
mixture of yellow and blue. Suppose the little spots where the blue touches 
under the translucent film to be so small as to be called molecules, and 
suppose the same of the spots where the yellow pigment touches, and you 
have all the conditions necessary for begetting green. It is also easily 
imagined how by regulating the amount of muscular pressure the propor- 
tions of the separate pigments is regulated, and so the most delicate tints 
are produced. 
Digestion in Insects. — A contemporary states that M. Plateau finds that 
