420 SCIENCE PROGRESS. 



occurring in organic nature, both in their genesis and in 

 their physiological, possibly indeed in their physical, sig- 

 nificance, arise from a single cause, and go back to a single 

 substance which is amalgamated with the original proto- 

 plasm and which in its further development and differenti- 

 ation follows the simple spectral colours in the order of the 

 rainbow. These be brave 'orts, but the author supports 

 them, at all events to some extent, by many curious obser- 

 vations on colour phenomena, which he arranges, for his 

 purpose, in three categories. First, he considers the psycho- 

 physiological evidence of vision. He states that with in- 

 creasing decomposition of rhodopsin (visual purple) a series 

 of colours is produced, running back to the primitive 

 colour. Second, in a similar sense, he remarks the frequent 

 change of colour in animals removed from shallow to deep 

 water. Certain worms (strudelwurmer) have black-brown 

 eyes in the former, whilst at great depths of the sea the 

 colour is red (38). So, too, the algae (Florideae) growing at 

 the greatest sea-depths are red. A similar change to red is 

 to be met with in animals and plants at high altitudes. These 

 Simroth interprets, not as phenomena of adaptation, but 

 of reversion. Third, the more complicated colour phenomena 

 are most marked in animals, whereas in plants, whose 

 metabolism is less active, the simpler spectral colours pre- 

 dominate. In plants too a change from yellow to green, 

 from xanthophyll to chlorophyll is consequent on aug- 

 mented metabolism ; a change in the opposite sense mark- 

 ing a falling off of metabolism. 



Even here Simroth does not reach the end of his 

 speculative tether. He suggests that the cause of the 

 nature of the primary pigment was either that in the 

 earliest times the atmosphere was more watery and 

 denser and thus let only the red rays through, or that 

 protoplasm could at first only respond to the longer 

 wave-lengths. 



For botanists, the chief interest of this paper, the con- 

 firmation of the main points of which would naturally 

 require far stronger and more exhaustive evidence than is 

 vouchsafed, lies in the suorcrestion that in cases where no 



