Xll CONTENTS. 



PAGE 



tion of nerve fibers, 46; elimination, 47; union, historic factor. V. Xeuromeres 

 and metamarism, 49. VI. Primitive sense buds, 50. 



CHAPTER IV. 



THE SUBDIVISIONS OF THE BRAIN . . 53~/o 



I. The prosencephalon, or forebrain, 53; the procephalic lobes, division into three 

 metameres; acilius, the hemispheres, optic ganglia and ocelli; arachnids, 54; the 

 olfactory lobes of the first segment; the hemispheres of the second; the forebrain 

 flexure. II. The diencephalon, 57; diencephalic flexure, cheliceral nerves and 

 ganglia, minute structure in limulus, 58; the large basal association neurones, 

 the large association neurones on the hemispheres, the cortex neurones; the cheli- 

 ceral lobes; the forebrain and cheliceral commissures; the stomodaeal ganglia and 

 the supra-stomodaeal commissure, 60; nerves to labrum; association with the coxal 

 taste organs; comparison with vertebrates, 60; summary, 64; III. The mesen- 

 cephalon, 65; the oral and hyoid arch neuromeres; mesenccele, 66; comparison of 

 thoracic neuromeres of arachnids with the midbrain neuromeres of vertebrates, 66. 

 IV. The metencephalon, or vagus neuromeres, and V. the branchiencephalon, 

 67; the vagus zone in arthropods, its special sensory characters; the branchience- 

 phalon, 69; the branchiencephalic neuromeres, number, segregation of their nerves 

 into branchial, cardiac, intestinal, hypobranchial, or branchiothoracic, 70. 



CHAPTER V. 



MINUTE STRUCTURE OF THE BRAIN AND CORD OF CERACHNIDS 7 l ~93 



Methods, 71. I. The branchial neuromeres of limulus, 71; development, 71; 

 commissures, 72; peripheral nerves, 72; cell clusters, 73; nerve roots, 76; branchial 

 nerve roots, haemal roots, 77; commissures, 79; the neuropile centers, 79. II. 

 The cephalic neuromeres, 80; haemal commissures, 81; haemal roots, 81; cranial 

 ganglia, 81; motor neurones, 84; gustatory nerves and tracts, 84. III. Longitudi- 

 nal tracts, 85; longitudinal haemal tracts, 85; longitudinal neural tracts, 86; the 

 lateral or pedal ganglion tracts, 86; the general cutaneous tracts, 87; comparison 

 with vertebrates, 87. IV. Commissures; summary, 90. V. The neuroccelia, 92. 

 VI. The neuroglial 93, 



CHAPTER VI. 



PERIPHERAL NERVES AND GANGLIA . 94-109 



I. Components of a neuromere, 94. II. Nerves of the diencephalon and mesen- 

 cephalon, 94; A. neural nerves, 94; the flabellum, 94; the cranial ganglia, 95; the 

 ganglia of the cord, 97; the haemal nerves, 97; the lateral line nerve of the chele- 

 ceral neuromere, 97. III. Nerves of the metencephalon, 98; limulus, neural nerves, 

 98; chilarial, opercular, haemal nerves; scorpion, 101; neural and haemal nerves, 

 longitudinal abdominal, 104; general cutaneous, io5;cardiac and hypobranchial 

 longitudinal abdominal, 104; general cutaneous, 105; cardiac and hyppobranchial 

 nerves. V. Relation of vagal and hypobranchial nerves in arachnids to those in 

 vertebrates, 107. 



CHAPTER VII. 



GENERAL AND SPECIAL CTUANEOUS SENSE ORGANS .... 110-124 



I. General cutaneous sense organs, no; temperature organs, no; free nerve ends, 

 in. II. Special cutaneous sense organs, in; the gustatory organs of limulus, 



