436 STELLA B. VINCENT 



tions were caused by the use of a high concentration of acids 

 which disrupted the permanently embryonic cells of the germi- 

 native layer in the skin of amphibians and fishes. He bases 

 his conclusions upon experimental behavioristic evidence and 

 micro-chemical studies. 



Sayle studied (24) the reactions of Necturus to stimuli through 

 the skin. She found it everywhere sensitive to tactile and chem- 

 ical stimulation, although some parts were more sensitive than 

 others. When any part was fatigued for a given chemical it 

 rarely responded to tactile stimulation although it usually re- 

 acted to other chemicals. Both the eyes and skin are photo- 

 receptors and the stimulation of cither brings about a negative 



reaction. 



VISION 



Birds — and mammals. — Two years ago, it may be remem- 

 bered, Johnson published the first of an admirable series of 

 articles on visual discrimination in vertebrates. These are 

 followed, this year, by three others (13). The previous experi- 

 ments determined the width of striae in a field which could 

 be distinguished as striae at a given distance under experimental 

 control. Paper III reports an attempt with the same animals, 

 a monkey and two chicks, to ascertain what differences in the 

 width of two systems of striae, both of which have proved 

 distinguishable, are necessary to effect discrimination. He found 

 that the monkey could distinguish differences in width of striae 

 of less than 3%. This is quite comparable with human ability 

 but roughly is ten times greater than the ability shown by the 

 chick 2. In the next experiment the differences in the direction 

 of the striae furnished the basis for discrimination. The mon- 

 key's difference threshold for direction of elements of a pattern 

 lay between 2° and 5°, the chick's between 25° and 40°. The 

 relative improvement brought about by training was much 

 greater in the monkey than in the chick. The third paper 

 gives a carefully controlled demonstration of the dog's deficiency 

 in detail vision and ascribes these factual results to the relative 

 inscnsitivity of the retina to the differences of distribution of 

 orightness over it. 



The spectrum of the domestic fowl is the subject of a study 

 by Lashley (16), who says: " The present paper offers further 

 evidence for the existence of color vision in the fowl, in the 



