 Parry ( 1975 ) described how this species has a wider range of eye movement than other snakes . Along a horizontal plane , eye movement can be maintained even if the head is rotated up or down to an angle of up to 45 ° . If the head is rotated 360 ° , one eye will tilt up and the other down , depending on the direction of rotation . Also , if one eye looks forward , the other looks back , as if both are connected to a fixed position on an axis between them . In general , the eyes often flick back and forth in a rapid and jerky manner . When asleep , there is no eye movement and the pupils are strongly contracted . The pupils dilate suddenly and eye movement resumes when the animal wakes up . 
 Parry ( 1975 ) described how this species <a href='got' title='1'><mark>has</mark></a> a wider range of eye movement than other snakes . Along a horizontal plane , eye movement can be maintained even if the head is rotated up or down to an angle of up to 45 ° . If the head is rotated 360 ° , one eye will tilt up and the other down , depending on the direction of rotation . Also , if one eye <a href='uninflect' title='2'><mark>looks</mark></a> forward , the other <a href='uninflect' title='3'><mark>looks</mark></a> back , as if both are connected to a fixed position on an axis between them . In general , the eyes often flick back and forth in a rapid and jerky manner . When asleep , <a href='dey_it' title='4'><mark>there</mark></a> is no eye movement and the pupils are strongly contracted . The pupils dilate suddenly and eye movement <a href='uninflect' title='5'><mark>resumes</mark></a> when the animal <a href='uninflect' title='6'><mark>wakes</mark></a> up . 
Parry ( 1975 ) described how dis species got a wider range of eye movement than other snakes . Along a horizontal plane , eye movement can be maintained even if da head is rotated up or down to an angle of up to 45 ° . If tdahead is rotated 360 ° , one eye gon tilt up and thdather downn , depending on thedarection of rotation . Also , if one eye look forward , the other look back , as if both r connected to a fixed position on an axis between them . In general , the das often flick back and forth in a rapid and jerky manner . When asleep , it ain't no eye movement and the pdals are strongly contracted . The pupils dilate suddenly and eye movement resume when the animal wake up .