REPORT OF COMMISSIONERS OF INLAND FISHERIES. 61 



As a basis for observations upon the nature of the discontinuous 

 variation of the early stages, experiments were tried which seemed to 

 demonstrate that, while the yellow pigment cells are slightly in- 

 fluenced by light and heat, these stimuli tend to produce a marked 

 expansion of the red chromatophore systems. Darkness artifically 

 brought to bear upon large numbers of first and second stage larvae 

 in which red pigmentation was developed especially well resulted, 

 with very few exception, in the contraction of the pigment into the 

 chromatophore centers and in the regaining of the homogeneous 

 blue coloration due to the soluble, diffuse pigment in the blood. 

 Although in many cases the expansion of the red chromatophores 

 followed as a result of putting the pale blue lobsters in the bright light, 

 these results were less constant in occurrence and the changes re- 

 c[uired a longer period. Nightfall and sunrise appear to be signals 

 for a change in the color of the first three larval stages. Those ob- 

 served in the daytime, if the light was bright, were, as a whole, well 

 pigmented with red, while, those observed at night showed the chro- 

 matophores in a greater state of contraction. This diurnal flood 

 and nocturnal ebb of pigment is characteristic of many of the higher 

 Crustacea. t 



First and second stage larva?, which were starved for some time, 

 seemed to present red pigmentation to a greater degree. Repeated 

 electrical stimuli also, in the majority of instances, gave similar 

 results. Both of these facts would be in accordance with the theory 

 that the occurrence of red pigment and the extension of the red 

 chromatophores is due, or, to say the least, is associated with periods 

 of weaker physical condition. This theory is partially substantiated 

 by the fact that lobsters of all stages, from old adults down to the 



sensitive chromatophores of the pigment-producing epithelium do not appear to be the agent 

 of adaptation to surroundings; indeed, it is very doubtful if the chromatophores themselves 

 undergo any marked change due to penetration of light through the thick, calcerous exoskeleton 

 of the adult lobster. Thus if we assume that the phenomenon of protective or adaptive colora- 

 tion is manifested in the adult lobster, the principle involved in the color change is very different 

 from that attributed by Pouchet to the protective color changes — "chromatic function" — 

 which he found manifested in many young larval Crustacea — changes which he believed to be 

 brought about through the medium of the nervous system and its action on the chromatophore 

 centers. 



t Keeble and Gamble. 



