1Any of a series of openings between the gill arches of a fish, through which water passes from the pharynx to the exterior, bathing the gills in the process.
- ‘One small gill slit is found in front of each pectoral fin.’
- ‘They have long ugly snouts and gill slits which seem almost to encircle the whole head.’
- ‘Water is taken in through the spiracles, passed over the gills, and expelled through the gill slits on the underside of the body.’
- ‘Adults are uniformly brownish gray, shiny on top and pale on the ventral side and around gill slits.’
- ‘Water exits through the gill slits at the back of the head.’
2A set of grooves similar to gill slits found in embryos of higher vertebrates.
- ‘Thus, the gill slits of the early human embryo supposedly repeat our distant ancestral past as a fish, while the transient embryonic tail, developing just afterward, marks the later reptilian phase of our evolutionary ascent.’
- ‘For Darwin, such apparently useless phenomena as the human appendix, or the tail and gill slits of the early stages of the human embryo, were signs of our evolutionary history.’
- ‘Another myth is the claim human embryos go through a fish-like stage and display gill slits.’
- ‘This may be illustrated by the gill slits in the embryos of higher vertebrates like reptiles, birds and mammals.’
- ‘Although they retain the chordate characters as adults gill slits are present only in the embryonic stages of land vertebrates.’
We take a look at several popular, though confusing, punctuation marks.