21. Manufactured retroreflectors modeled after a " tapetum lucidum " are described in numerous patents and today have many uses. 22. Some species have a tapetum , a reflective layer which bounces light that passes through the retina back through it again. 23. Pollen structure shows that of the two main tapetum types, secretory and plasmodial, the lilioid monocots are nearly all secretory. 24. Eyeshine is the result of a light-gathering layer in the eyes called the tapetum lucidum, which reflects white light. 25. Similar adaptations occur in some species of spiders, although these are not the result of a " tapetum lucidum ". 26. Most primates, including humans, lack a " tapetum lucidum ", and compensate for this by perceptive recognition methods. 27. When light shines into the eye of an animal having a " tapetum lucidum ", the pupil appears to glow. 28. The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. 29. The tapetum lucidum, in animals that have it, can produce eyeshine, for example as seen in cat eyes at night. 30. Some species are able to effectively turn their tapetum off in bright conditions, with a dark pigment layer covering it as needed.
