THE CLASS GEPHYREA. 243 



the belly. The teeth are not well developed. It appears to be terrestrial in its habits sometimes. 

 They are common in Egypt, and the soldiers of Napoleon suffered much from them in his campaign. 

 They also attacked the horses and cattle. These must not be taken for true Leeches, some species of 

 which, especially in the tropics and even to the north, lead a life amongst damp vegetation, and 

 attack Europeans with great ardour. Such are the Leeches of the Himalayas, Ceylon, the Philip- 

 pines, Arc. 



Another so-called Horse Leech belongs to the genus Aulostomum, but it does not appear to suck 

 blood or to worry horses. 



The glutton Aulostome, writes Dalyell, " is an active, bold, and clever animal, frequently 

 crawling out of the water, and apparently always ready to quit the vessel. None of the tribe surpasses 

 it in voracity. Few animal substances are rejected. All kinds of fish, dead or alive, seem acceptable. 

 Penetrating the cavity of the larger fresh-water shells, this Horse Leech takes up a permanent 

 dwelling there, until emptying them of their contents, should it be able." The same author notices 

 that these Leeches are cannibals, and that they will swallow even dead Leeches of different kinds. It 

 feeds on Earth Worms, Grubs, and Snails. It has a long intestine with only two cseca. The genus 

 Bdella has an oval sucker and four pairs of eyes, and is African, and the species of Nephelis have 

 thin bodies and no jaws. One of these is the Eight-eyed Leech of ponds and lakes, and is a very 

 active animal. It moves with an undulating movement, does not quit the water, and often fixes 

 itself by the terminal sucker, and waves the body to and fro. They are carnivorous, and yet do not 

 prey like the carnivorous Leech. They attack almost every small animal that comes in their way, and 

 swallow it, more or less whole, by placing the sucker over it and then dilating their gullet. Small 

 Mollusca, Earth Worms, Planarise, and even their fellows, are readily devoured. They are small, being 

 from one and a half to two inches long and two or three lines broad. They are usually brown in 

 colour, and may be speckled with yellow dots. They deposit their eggs in capsules, each of which 

 contains from six to twenty ova, embedded in a gelatinous mass. 



CHAPTER II. 



THE GEPHYKEA, THE WHEEL ANIMALCULES, THE ROUND AND THREAD WORMS, 



THE FLAT WORMS. 



GEPHYKEA Bolster-shaped Worms Characters- ROTIFERA, THE WHEEL ANIMALCULES Structure Classifica- 

 tion The Philodinidae The Brachionidse Other Families THE NEMATHELMINTHA, ROUND AND THREAD 

 WORMS Characters The Thorn-headed Worm THE THREAD WORMS The Genus Trichina The Trichina 

 spiralis Description Reproduction Their Effects The Whip Worm The Genus Filaria The Guinea Worm 

 The Ascaris The Lung Worm The Genus Mermis THE FLAT WORMS The Tape Worms Characters Repro- 

 duction The Beef Worm THE TREMATODA THE TURBELLARIA Classification of Vermes. 



CLASS GEPHYPtEA. 



THERE are many kinds of Marine Worms which resemble at first sight the Holothuria, or Sea Cucum- 

 bers, belonging to the Echinoderrnata (see Fig. 17, p. 272). Their bodies are usually long, cylindrical, 

 without u feet," and there is no distinct separation into segments. A little trouble distinguishes the 

 group, for the Gephyrea have neither calcareous bodies in their, skin nor ambulacral regions on the 

 body. These bolster- shaped Marine Worms live at great depths, with their bodies in the sand or mud 

 or under stones. Some exist in the shells of Mollusca, and others in the interstices between corals. 

 Footless, without a series of lateral bristles and suckers, these worms have their locomotion singularly 

 defective ; but a great many species have a proboscis, which is more or less retractile, and which 

 is terminated by the mouth, and it may be used as an organ of prehension, and, to a certain extent, of 

 locomotion. It is said that some species * perforate limestone ; others certainly penetrate soft clays,f 

 and one group, which has a crown of tentacles formed by numerous branchial filaments, resides in tubes. \ 

 The species of Bonellia lead a more or less wandering life. When one of these Gephyrea is placed in 

 water, after a while it elongates and appears to be soft, and the trunk or proboscis is put forth, 

 * Genus Thalassema. f Genus Phoronis. J Species of Sipunculus. 



