INSECTA. 207 



tjjjc in the perfect state, as in the species of butterfly described by 

 Heroldt, it will be found to correspond with the sixth stage figured by 

 this author in the pupa of the Papilio hrassicce. 



In the predatory leaf insect (^Mantis) the progress of coalescence 

 has reduced the number of abdominal ganglia to four, the three tho- 

 racic ganglions continuing distinct, so that the nervous system cor- 

 responds with the eighth stage figured by Heroldt in the Lepidop- 

 terous insect just mentioned. The supra-oesophageal mass consists of 

 two triangular lobes having their bases rounded and anterior, and 

 their apex prolonged into the oesophageal chords. Two small nerves 

 are sent off from the anterior part to the ocelli, where they swell into 

 a slight enlargement. Two short and thick optic nerves pass from 

 the sides of the brain to form the ganglions supplying the large com- 

 pound eyes. 



The stomato-gastric nerves arise, one on each side, near the optic 

 nerves. The oesophageal columns are short, and directly converge to 

 the inferior cerebral ganglion, which gives two large and several 

 small nerves to the jaws : it is situated in the head. Two long and 

 parallel columns extend to the first thoracic ganglion, which trans- 

 mits long and large nerves to the formidable prehensile anterior pair 

 of legs. The second thoracic or elytral ganglion is at a great dis- 

 tance from the first, and much nearer the third or alar ganglion. 

 Anastomosing branches connect the nerves which these ganglions 

 respectively distribute to the elytra and wings. The Mantis is 

 chiefly remarkable for the great length of the ventral chords con- 

 necting the brachial with the elytral ganglia, and which renders 

 them favourable for minute analysis of their structure. Anterior and 

 jiosterior columns, or divisions analogous to those in the spinal mar- 

 row of higher animals, cannot be distinguished. The so-called sen- 

 sorial tract is confined to accumulations of nervous matter at the 

 origin of the nerves to the locomotive organs. 



The results of the experiments in which the body of the living 

 Mantis has been so divided, that a segment with one of these 

 ganglionic enlargements and the locomotive organs it supplies has 

 been detached fi'om the rest, illustrate the functions of the aggre- 

 gated centres of nervous matter in relation to their power of receiving 

 and transmitting impressions, so as to maintain the order of action of 

 such detached organs upon the application of a stimulus, for a con- 

 siderable period after the mutilation. 



The jaws of the separated head of a Mantis bite forcibly the stick 

 which is held to them. The formidably armed prehensile legs in 

 like manner wound the finger that touches them, when the segment 

 of the body supporting them is separated from the head and tiie rest 



