618 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Chromatopliores of Animals.* — Mr. W. Garstang lias an interesting 
general article on the chromatopliores of animals. He defines chromato- 
phores as pigmented cells specialised for the discharge of the chromatic 
function. Their evolution cannot be adequately considered, except by 
the comparative method, which in this case involves a survey of pigment- 
cells in general. In this survey special attention has been paid to two 
points : (1) The localisation of the pigment-cells and their relation to 
the germinal layers ; (2) The nature of the structural modifications 
exhibited by pigment-cells. Although these cells are widely distributed, 
they attain a high elaboration of form and function in relatively few phyla. 
In the Animal Kingdom, the only pigment-cells distinctly specialised 
for chromatic purposes are those of Vertebrates, of Oephalopod and of 
certain Pteropod Mollusca, and of Crustacea. It would appear that 
there is a considerable amount of evidence in favour of the view that 
chromatopliores in general are of ectodermal origin, whatever be their 
ultimate position in the body. Mr. Garstang is astonished at discovering 
that there is not within the whole of the existing literature a single 
indubitable proof of the mesodermal origin of the true chromatic cells. 
A classification is suggested which indicates the relation of the different 
kinds of chromatophore. 
I. Autoplastic form, changes intrinsic. 
(1) Holoplastic, contractile as a whole, 
e. g. Ctenophora, Isopoda. 
(2) Endoplastic, inner protoplasm alone contractile, 
e. g. Vertebrata, certain Pteropods. 
II. Alloplastic form, changes extrinsic, 
e. g. Cephalopoda, certain Pteropods. 
Bibliography of North- American Paleontology, f — Mr. C. R. Keyes 
has prepared a Bibliography of North- American Palaeontology for the 
years 1888 to 1892. In addition to an authors’ list, in which a brief 
synopsis of the contents of each paper is given, there is a title index in 
which the name of each article appears under each of its leading words, 
and there are in addition subject entries and cross references. These 
are biological, geological, and geographical. It is claimed that- one of 
the principal advantages of the present scheme is that in no case is it 
necessary to turn back from title to title in order to obtain a full biblio- 
graphical reference. A worker upon any systematic group of animals, 
a particular geological age, or a given area, finds all the articles upon 
the subject brought together. If this bibliography proves to be trust- 
worthy, it will be indeed a most valuable handbook. 
XNVEHTEBHATA. 
Distribution of Aquatic Invertebrates. t — Hr. 0. E. Imhof gives a 
series of tables showing the distribution of “ Aquatilia invertebrata ,r 
in Switzerland. He distinguishes subnival, alpine, upper forest, lower 
forest, and valley regions, and deals almost exclusively with Molluscs. 
* Science Progress, iv. (1895) pp. 104-31. 
f Bull. U.S. Geol. Survey, cxxi. (1894) 251 pp. 
t Biol. Centralbl., xv. (1895) pp. 713-9. 
