94 On Animal Chlorophyll. [February, 
means of the diffused green colouring-matter of their edto- 
plasm, of evolving oxygen under the stimulus of light. 
Thus we have here the first undoubted animals which assi- 
milate by means of a chlorophyll forming part and parcel 
of their own living structure, and not by the mediation of 
vegetable guests. 
The fa<5t that the badterial reaction, as regards its slight 
intensity, may be compared with that of Infusoria, which 
harbour living chlorophyll granules to some extent, is ex- 
plained by Engelmann by the consideration that the assimi- 
lating colouring-matter was present only in very small 
quantity. Further, the Vorticellae themselves consume 
much of the oxygen liberated, so that they can throw off 
but little externally. The Vorticellae, indeed, as the author 
has proved by a series of observations, have a great need of 
oxygen, — a fadt which agrees well with the supposition that 
they can prepare a supply for themselves. 
Herr Engelmann has instituted further experiments in 
order to decide whether the colouring-matter of these animal- 
cules is identical with the chlorophyll of plants, or whether 
it is a peculiar and merely analogous chromophyll. To this 
end the assimilative energy in the various colours of the 
spedtrum was tested by means of the “ Badteria-method.” 
Its behaviour was found similar to that of the green colour 
of plants. The colouring-matter was next obtained in the 
form of globules, and examined with the spedtroscope. 
There was found a well-marked absorption-band in the red, 
between B and C, and an absorption at the extremity begin- 
ning with F. These peculiarities testify for the identity of 
the colour of the Vorticellae with vegetable chlorophyll. 
Finally a series of chemical readtions were applied, espe- 
cially that of concentrated sulphuric acid. The results still 
confirmed the identity of the two colouring-matters. 
It is to be regretted that the scarcity of green Vorticellae 
put for the present an end to these researches. In the 
meantime the fadts ascertained suffice to put an end to the 
dodtrine of the exclusively vegetable nature of chlorophyll. 
Even if it could be proved that the pigment of these Vorti- 
cellae was ultimately derived from a vegetable source the 
fundamental principle would remain unaffedted. For the 
principle is that there are animals which by means of a 
pigment combined with their own living plasma, and not to 
be distinguished from the chlorophyll of plants, are able to 
assimilate under the stimulus of light exadtly as do green 
vegetables. 
It is not probable that the green Vorticella is the only 
