1899] A THEORY OF COLOUR VISION 189 



that these necessary fibrils have never been discovered in human eyes 

 which we know for certain have a scale of colour sensation, we would 

 remind Dr. Patten that the little evidence which we have — however 

 unsatisfactory we admit it to be — points rather to the tips of the rods 

 or cones as being sensitive to red, and the bases to the violet, which is 

 the reverse of what his theory demands. Nor again do we admit that 

 " every one knows " that the nerve fibres are discontinuous, as taught 

 among others by Eamon y Cajal. It is true that this doctrine has 

 been very hastily accepted, but signs of reaction are not wanting. 



One curious part of Dr. Patten's theory is that the optic ganglion, 

 having in some animals (e.g. Acilius) a slight resemblance in shape to 

 the retina, and its " Punct-substanz," and being composed of similar fine 

 "vibrating" fibrils, forms with the retina an apparatus suggestive of 

 " a Marconi transmitter and receiver " ! 



Adaptation. 



Under the title " Zweckmiissigkeit und Anpassung," Dr. J. W. Spengel 

 has published, with Gustav Fischer of Jena, a recent academical address. 

 In popular language adapted to a mixed audience, he here discusses 

 one of the vexed problems of evolution. Finding plants and animals 

 fitting perfectly into and reacting with their surroundings, like " ready- 

 made machines dropped down from heaven," we have, alas ! no certain 

 answer to the question " how they came there." While admitting 

 that we must use the word " adaptation," it is yet, to the author, 

 one of these beautiful words which always pop up " wo Begriffe 

 fehlen," as Goethe's Mephistopheles points out to encourage students 

 of theology. Let us be clear then what we mean. Does " Adaptation " 

 mean " adapted from without " or " adapting itself from within ? " In 

 very limited and quite unimportant matters the word may be admitted 

 in both senses. But to show how inadequate these are to explain the 

 facts, he gives a list of cases in which he contends neither would 

 apply. One such case, for example, is the perfect fitness of the whale 

 to its marine life in cold latitudes. In reference then to the essential 

 mechanics of evolution the word adaptation does not mean a process 

 but a fact. His "Anpassung" is therefore nothing more than his 

 " Zweckmiissigkeit," and he looks elsewhere for its explanation. 



The best answer, he concludes, is that given by the " Natural 

 Selection " of congenital variations. It may be doubted, however, 

 whether Dr. Spengel's arguments against direct modification of 

 structure in response to changes in the environment, and the gradual 

 inheritance of these modifications, attain that degree of cogency which 

 can be called convincing. 



