Relation of Higher Animals to Man 553 



body, though usually encased in a hard chitinous exoskeleton, 

 is brought fully and delicately into tactile — perhaps even other 

 stimulation — relations by abundant nerve hairs that pass 

 through holes in the chitinous layer. 



The nervous system, in the more generalized forms, is an 

 elongated double cord, with supra- and sub-oesophageal ganglia, 

 also added ganglia that are scattered along the ventral cords. 

 With increasing specialization and diversity of environal con- 

 tact the first two of these ganglia steadily enlarge till they 

 greatly exceed the others in size and complexity. It is there- 

 fore quite exact in such a case to speak of the mass as a brain. 

 This brain even in high insect individuals of the same species 

 may vary according to use. Thus Brandt finds that "the abso- 

 lute size is not a criterion for the amount of intelligence, and 

 we must rather look to the complication of the structure and 

 to the development of certain parts for an index of this nature. 

 The drone in the honey-bee has, correlatively with the superior 

 development of its eyes, a larger brain than the worker, but 

 the size of the hemispheres and the development of the gyri 

 cerebrales are superior in the latter. In other words the mass 

 of those great lobes of the brain that are directly connected 

 with the faceted eyes must not be taken into account in con- 

 sideration of the relation of the size and development of the 

 brain to the intelligence of the individual" (181: 119). 



As regards brain-weight in relation to body-weight Lowne 

 (176: 120) has found that in insects it may vary from 2500 

 to as much as 155. In man the proportion is 35 to 45 while in 

 the higher apes it varies from jeo to jgo- The brain of the ant 

 fills a large part of the head, and as figured and described by 

 Leydig, is of highly complicated structure. The muscular 

 system is also powerfully developed, and the striped muscle 

 fibers of some insects — not least the ants — are amongst the 

 most perfect in the animal kingdom. Thus have resulted 

 the powerful tugging, lifting, shouldering, carrying, and other 

 movements that one often witnesses in watchhig ants on their 

 hills, or along their pathways. 



Now if we concentrate attention on the brown or allied ant, 

 every movement of the body indicates that it is constantly 



18* 



