Nemertines sentence example
- Nemertines live in the sea, some being common amongst the corals and algae, others hiding in the muddy or sandy bottom, and secreting gelatinous tubes which ensheath the body along its whole length.
- Burger classifies Nemertines into four orders: I.
- In Nemertines the everted proboscis is retracted in the same way as the tip of a glove finger would be if it were pulled backwards by a thread situated in the axis and attached to the tip. The comparison may be carried still further.
- It is worthy of notice that in those Nemertines which make a very free use of their proboscis, and in which it is seen to be continually protruded and retracted, the walls of the proboscidian sheath are enormously muscular.
- The omnipresence of this connective tissue tends to exclude the formation of any perivisceral body cavity in Nemertines.Advertisement
- At the same time it renders more intelligible the extreme sensitiveness of the bodywall of the Nemertines, a local and instantaneous irritation often resulting in spasmodic rupture of the animal at the point touched.
- With respect to the sense organs of the Nemertines, we find that eyes are of rather constant occurrence, although many Heteronemertines living in the mud appear to be blind.
- The anterior opening, the mouth, is situated ventrally, close to the tip of the head and in front of the brain in the Metanemertini, somewhat more backward and behind the brain in the other Nemertines.
- It is a curious feature in Nemertines that the alimentary canal seldom contains traces of food and yet most of these worms are voracious.
- Its presence is one of the most distinctive features which separate the Nemertines from the Platyhelminthes.Advertisement
- In the Nemertines the sexes are separate, with only very FIG.
- Development.-The embryology of the Nemertines offers some very remarkable peculiarities.
- In the latter we find the young Nemertines crawling about after a period of from six to eight weeks, and probably feeding upon a portion of this gelatinous substance, which is found to diminish in bulk.
- Affinities.-The position of the Nemertines in the animal kingdom is now looked upon as more isolated than was formerly thought, and recent writers have been inclined to treat them as a separate phylum.
- Whether this view be adopted or not, and whether the Turbellaria be regarded as nearly related or only remotely connected, there can be little doubt that the Nemertines resemble the Turbellaria more nearly than they do any other group of animals.Advertisement