Chaetopod Sentence Examples
Ray Lankester to the members of a series of tubes, proved in some cases to be excretory in nature, which exist typically to the number of a single pair in most of the segments of the Chaetopod body, and open each by a ciliated orifice into the coelom on the one hand, and by a pore on to the exterior of the body on the other.
H, The acrembolic (= pleurecbolic) pharynx of a Chaetopod fully introverted.
This statement is quite consistent with the continuous production of new segments at the neck of the scolex, for such a process is analogous to the development of the segments in a Chaetopod, which is a perfectly distinct phenomenon from the regeneration of new segments to supply the place of a head or tail-end or some other portion that has been lesioned.
It exactly agrees with the larval form of many Chaetopod worms and other Coelomata.
It is held by some morphologists that the mollusc body is unsegmented, and therefore is to be compared to a single segment of a Chaetopod or Arthropod.Advertisement
The figure on the left represents the condition in a Chaetopod, that on the right the condition in an Arthropod.
A similar constitution of the body is more clearly seen in the Chaetopod worms. In the Vertebrata also a repetition of units of structure (myotomes, vertebrae, &c.) - which is essentially of the same nature as the repetition in Arthropods and Chaetopods, but in many respects subject to peculiar developments - is observed.
The reduction of the outgrowth-bearing " corm " of the parapodium of either a Chaetopod or an Arthropod to a simple cylindrical stump, devoid of outgrowths, is brought about when mechanical conditions favour such a shape.
The Arthropod eye appears to be an organ of special character developed in the common ancestor of the Euarthropoda, and distinct from the Chaetopod eye, which is found only in the Onychophora where the true Arthropod eye is absent.
The essential difference between these two kinds of eye appears to be that the Chaetopod eye (in its higher developments) is a vesicle enclosing the lens, whereas the Arthropod eye is a pit or series of pits into which the heavy chitinous cuticle dips and enlarges knobwise as a lens.Advertisement
On the hypothesis that such a form as Dinophilus (see Haplodrili) has preserved the characters of the primitive Chaetopod more nearly than a any existing Polychaet or Oligochaet, it is clear that the nephridia in the Oligochaeta have preserved the original features of those organs more nearly than most Polychaeta.
The " introvert " in these Gastropods is not the pharynx The ctenidium is monopectinate and attached to the mantle along as in the Chaetopod worms, but a prae-oral structure, its apical limit being formed by the true lips and jaws, whilst the apical limit of the Chaetopod's introvert is formed by the jaws placed at the junction of pharynx and oesophagus, so that the Chaetopod's introvert is part of the stomodaeum or fore-gut, whilst that of the Gastropod is external to the alimentary canal altogether, being in front of the mouth, not behind it, as is the Chaetopod's.