10 GLOSSARY. 



Ap'tychi (Gr. apto, I fasten). Plates of shelly substance found 

 sometimes in the terminal chamber of Ammonite shells. 



Aquaeduc'tus coch'leae (L. aqueduct of the cochlea). A small 

 canal leading from the cochlea of the human ear to the 

 jugular fossa of the petrous bone. 



Aquseduc'tus Fallo'pii (L. aqueduct of Fallopius). The canal 

 in the temporal bone which transmits the facial nerve. 



Aquaeduc'tus Syl'vii (L. aqueduct of Sylvius). A narrow 

 canal connecting the third ventricle of the brain with its 

 fourth ventricle, so named from its discoverer. 



Aquaeduc'tus vestfbuli (L. aqueduct of the vestibule). A 

 small canal leading from the vestibule of the human ear 

 to the posterior surface of the petrous bone. 



Aqueous (L. aqua, water). Watery. Applied to the humour 

 filling the anterior chamber of the eye. 



Aquiferous canals (L. aqua, water; fero, I carry). Water- 

 bearing. Small canals which in some molluscs traverse 

 the substance of the foot and open externally. 



Arach'nida (Gr. arachne, a spider). A division of the Ar- 

 thropoda which includes the spiders, scorpions, and 

 mites. 



Arachni'dial mammilla (Gr. arachnc, a spider ; L. mantilla, a 

 little teat). The teat-like terminations of the ducts of the 

 glands which secrete the web in the spiders. 



Arachnidial papillae (Gr. arachne, a spider; L. papilla, a 

 nipple). The terminations of the arachnidial mammillce. 



Arachni'dium (Gr. arachnc, a spider). The glandular organ in 

 which the web of spiders is secreted. 



Arach'noid (Gr. arachne, a spider's web). The serous sac which 

 forms the middle of the three enveloping membranes of 

 the brain and spinal cord. 



Aranei'na (L. aranea, a spider). The spiders. 



Ar'bor vi'tae (L. tree of life). The name applied to the tree- 

 like disposition of the grey and white nerve tissues in the 

 cerebellum, as seen in a vertical section. 



Archaeoptery'gidaB (Gr. archaios, ancient ; ptcryx, a wing). A 

 class of extinct Oolitic birds, of which at present only one 

 representative (Archaeopteryx) is known. 



ArchaeostS'matous (Gr. archaios, ancient, primitive; stima, 

 stitmatos, the mouth, entrance). A term applied to a 

 gastrula when the blastopore does not entirely close up, 

 but remains as the aperture by which the endodcrm of the 

 organism communicates with the exterior. 



