The Central Ganglia of Xenylla 



WILLIAM A. HILTON 



Serial sections were made through the entire animals of the 

 genus Xenylla of the family Poduridse. The length of the 

 animals after they were fixed and imbedded in paratfine was 

 about one millimeter. By means of longitudinal and cross sec- 

 tions the ganglia were studied. 



At this time the peripheral nerves and sense organs will 

 not be considered to any degree. This form has eyes, the 

 nerves supplying them are very short. The anterior and lateral 

 portions of the brain are connected with these organs. The 

 nerves to the antennae are from the lateral portions of the 

 supraesophageal ganglion. They are accompanied with nerve 

 cells for a short distance, as is shown in one of the figures. 

 Although no postantennal organ was found, there were some 

 evidences of a ganglion which seemed to correspond in position 

 to this structure which has been found associated with the 

 postantennal organ of Collembola. 



The general form of the central nervous system of Collem- 

 bola was perhaps first described by Nicolet in 1841. Three 

 ventral ganglia were recognized, two thoracic and one abdom- 

 inal. Sommer in '85 found four nerve centers below the head, 

 three of these are called thoracic and one abdominal. Lubbock 

 '73 found three ganglia in the thorax and abdomen of Tomo- 

 cerus. Linear species of Collembola are described as usually 

 having two thoracic and one abdominal ganglion. Fernald '87 

 in Anurida, recognizes pro-, meso- and metathoracic ganglia. 

 The last of these seems composed of two ganglia. 



There are a number of other papers which describe or figure 

 the complete nervous system of some species of Collembola. 

 Among the more recent of these are those of Philiptschenko 

 '12, Hilton '13. As a rule two chief cephalic ganglia are 

 described and three others in linear species. 



