THE EGG-LAYING APPARATUS IN THE SILKWORM 

 (BOMBYX MORI) AS A REFLEX APPARATUS 



BY 



ISABEL M'CRACKEN. 



(From the Physiological Laboratory, Stanford University.) 

 With One Figure. 



The earliest investigators of the nervous system of Arthropoda 

 (Alexander von Humboidt, 1797, Treviranus, '32, Bur- 

 MEISTER, '32) established several facts in regard to the functions 

 of the nervous system in insects. 



1. That the nerves of insects are as sensitive to electrical and 

 chemical stimuli as those of vertebrates. 



2. That correlated movements are not impossible after the 

 head has been snipped off (walking, sw^imming, etc.), although 

 frequently requiring external stimuli to initiate the movement. 



3. That removal of an eye, a feeler or half of the brain causes 

 circular movements tov^ard the sound side. 



These writers, however, looked upon the brain as the instigator 

 and controller of the functions of the nervous system and traced 

 the motions after decapitation to the irritability of muscles alone. 

 Not until Newport^ investigated the anatomy of the nervous 

 system of Sphinx ligustri did investigators begin to assume func- 

 tional independence for the ganglia of thorax and abdomen in 

 insects. Later investigators, notably Faivre ('56), Ward ('79), 

 Steiner ('87), and others, found the thoracic as well as the supra- 

 (the brain) and sub-oesophageal ganglia to be centers of move- 

 ment, and the abdominal ganglia to be respiratory centers at least. 

 Faivre claimed for the brain and for the sub-oesophageal ganglia 

 certain characteristic functions analogous to those of the brain of 

 vertebrates — for the brain, will and directive power, and for the 

 sub-oesophageal ganglion coordination of movement. 



* Newport, George, 1834. On the Nervous System of Sphinx ligustri. Philosophical Trans- 

 actions, p. 389. 



