Polarity in Organic Elements. 371 



condition of the sensory layer of the skin, which is shown in the abnor- 

 mal or deficient deposit of pigment in the eye. Pigment is an important 

 part of the machinery for receiving the light and turning it into sensa- 

 tion in the eye, and it is also thought by some to have a like influence 

 upon the waves of sound conveyed to the ear. ( Bain. ) Whether this 

 be true or not, since the senses are all founded upon the same sensory 

 layer, it appears probable that the defect which shows itself in the sense 

 of sight might also do the same in another sense. Albinos and white 

 animals are said to be less sensitive in both sight and smell, owing to 

 some deficiency in the skin which involves a lack of the requisite pig- 

 ment. According to Cuvier, the Camel, during the rutting season, ex- 

 udes a fetid humor from his head. This curious correspondence is 

 paralleled by the correlation between the horns and sexual functions of 

 deer. Horns are normally developed in the males only, in all the deer 

 species except reindeer. The rutting season immediately follows their 

 development, but if the male be emasculated no horns grow. "One 

 instance is recorded of a doe with a single horn, resembling that of a 

 three-year-old buck, and on dissection the ovary of the same side was 

 found to be scirrous," that is, indurated and functionally destroyed. 



It will be remembered that all animals pass through an hermaphro- 

 dite stage of sexual development in embryo life, both sorts of sexual 

 organs being started, and one set afterwards suppressed. In the case 

 of the female deer mentioned above, obviously the female organs on 

 one side only were brought forward, while their partial suppression on 

 the other allowed for a partial development of the male organs, includ- 

 ing the correlative horn. The possession of horns by the male deer 

 probably relate to their contentions with each other during the breeding 

 season, and have arisen by selection with reference to this competition. 

 This is supported by the fact that ' ' after attaining their maximum of 

 development the antlers of these animals decrease in old age at each 

 successive renewal, " that is, decrease with decreasing virility. The 

 " fetid exudation " from the head of the camel is doubtless the equiv- 

 alent of what in the other ruminants is hardened into horns, and by se- 

 lection turned into formidable weapons of defense. 



As a fair example of the correlation of interdependent parts may be 

 mentioned the cranial ridges of some of the anthropoid male Apes, 

 which are made necessary for the attachment of very large muscles 

 which work ponderous jaws, in which are set incisor and canine teeth 

 of extraordinary size. A similar sequence of correlations exists in the 

 Lion ; beginning with the great teeth each of the other parts follows as 

 a necessary accompaniment, ending with the cranial bony ridges. Sim- 

 ilar habits of life in the two animals have developed a similar formation 

 of parts, and the correlation of the parts is obviously due to their ac- 

 tion upon each other. 



