THE DEVELOPMENT OF CHROMATOPHORES IN NECTURUS. 
BY 
ALBERT C. EYCLESHYMER. 
From the Anatomical Laboratory of St. Lowis University. 
WITH 7 FIGURES. 
The questions regarding the origin of pigment in the epidermis of 
vertebrates is one of deep interest not only to the histologist, but also to 
the pathologist. 
The literature shows that two different conclusions have been reached. 
One group of workers (Aeby, Keelliker, Ehrmann, Ribbert and others) 
have regarded the epidermal chromatophores as modified mesenchymal 
cells, which have wandered into the epidermis. Another group (Kodis, 
Jarish, Kromayer, L. Loeb, Strong and others) have considered the epi- 
dermal chromatophores as modified epithelial cells which have differen- 
tiated in situ. 
In the course of my studies of the larve of Necturus, I have been re- 
peatedly attracted not only by the peculiar movements of the chroma- 
tophores in the normal embryo, but also by the striking changes in their 
character brought about through decapitation. 
These casual observations led to a new method of studying the origin 
and movements of chromatophores. The method was briefly the follow- 
ing: The larve were placed in a bed of cotton in the fibers of which they 
soon became entangled, and were thus held in a given position for an in- 
definite period. The water in the receptacle containing the cotton was 
of course frequently changed. The larve were then observed under the 
higher magnification of the binocular dissecting microscope, and the 
movements of the living chromatophores followed. This study was then 
supplemented by a study of serial sections of larve of corresponding 
stages. 
Larve 11-12 mm.—The first appearance of pigment is found in the 
larvee of this length. When observed under the binocular microscope, 
this pigment appears as minute black dots lying deep down in the trans- 
parent connective tissues. If these minute structures be persistently 
watched for a few hours, or even examined at short intervals, it is easily 
seen that they gradually increase in size and slowly approach the sur- 
face. When first observed, the pigment seems to be confined to the body 
AMERICAN JOURNAL OF ANATOMY.—VOL. V. 
