REPORT OF COMMISSIONERS OF INLAND FISHERIES. 79 



young larvae do not appear to be protective; and, moreover, the color 

 and coloration of later stage lobsters, which certainly do manifest 

 color adaptation to environment, appear to be influenced not so 

 much by chromatophore activity as by chemical changes in the ab- 

 sorbed pigments of the calcerous exoskeleton brought about by the 

 influence of light intensity or other environmental conditions. 



Chromatophore activity may be stimulated by light, heat, and 

 electricity, the resultant changes taking place most quickly in the lar- 

 val stages. These stimuli cause, under most conditions, expansion 

 of the chromatophore cells, while darkness and cold result in their 

 contraction. These changes which determine the color of the young 

 lobsters, as red or blue, result not only from the application of arti- 

 ficial stimuli, but, in the case of light, with the change from night to 

 day. Light intensity, rather than backgrounds, seems to condition 

 the ebb and flow of color pigment in Homarus. 



The phenomenon of rapid, transitory color changes is lost when 

 the lobster enters the fourth stage. This stage allows a wider range 

 of color variation than any following stage. The characteristic 

 color scheme includes yellow, red, and green, and the fourth stage 

 lobsters exhibit some variety of modification or of mixture of these 

 three main types. 



The characteristic color of the fifth stage lobster is a rich broicn, set 

 off by light spots varying in intensity from snow white to dirty yel- 

 low. These spots may occur on the tips of certain appendages or on 

 certain parts of the body where they usually mark the attachments 

 of muscles. The body transparency has disappeared almost wholly 

 in this stage; exceptions, however, may be noted. 



The color and coloration of the sixth stage lobster is hardly dis- 

 tinguishable from the preceding stage. Bands and spottings of 

 white are, however, usually more prominent in the sixth stage. 

 During the latter part of the stage the color often changes to a dark 

 drab, thus anticipating the stage succeeding. 



The color of the seventh stage lobster is very typical and char- 

 acteristic, slate, having as occasional variations, green-slate, hlue-slate, 



