Ommatidia sentence example
- Watase has shown, in a very convincing way, how by deepening the pit-like set of cells beneath a simple lens the more complex ommatidia of the compound eyes of Crustacea and Hexapoda may be derived from such a condition as that presented in the lateral eyes of Limulus and Scorpio.
- There are over 25,000 ommatidia in the eye of a hawk moth.
- In the specialized ommatidia of the compound eyes of Crustacea and Hexapods the rhabdom is an important structure.'
- - Section through a portion of the lateral eye of Limulus, showing three ommatidia - A, B and C. hyp, The epidermic cell-layer (so-called hypodermis), the cells of which increase in volume below each lens, 1, and become nerve-end cells or retinula-cells, rt; in A, the letters rh point to a rhabdomere secreted by the cell rt; c, the peculiar central spherical cell; n, nerve fibres; mes, mesoblastic skeletal tissue; ch, chitinous cuticle.
- They consist of a varying number of ommatidia or visual elements, covered by a transparent region of the external cuticle forming the cornea.Advertisement
- In most cases this cornea is divided into lenticular facets corresponding to the underlying ommatidia.
- The compound eye of the king-crab (Limulus) is the only recognized instance of ommatidia in their simplest state.
- In Crustacea and Hexapoda of all grades we find compound eyes with the more complicated ommatidia described above.
- But they seem to point to a community of origin of Hexapods and Crustacea in regard to the complicated ommatidia of the compound eye, and to a certain isolation of the Arachnida, which are, however, traceable, so far as the eyes are concerned, to a distant common origin with Crustacea and Hexapoda through the very simple compound eyes (monostichous, polymeniscous) of Limulus.
- It shows in Scorpio and Limulus a tendency to segregate into minor groups or " ommatidia."Advertisement