CARNIVOROUS ANNELIDS AND SIPHON-WORMS 149 



It must not, however, be supposed that all the jawed Leeches 

 are blood-suckers. Some of the terrestrial forms, for instance, 

 live upon earth-worms, and many of the aquatic species also live 

 upon small invertebrates. This is the case in the well-known 

 and much-slandered Horse- Leech {Aulastomum gulo), in which 

 the jaws are not nearly so well developed as in the medicinal 

 form. 



Jawless Leeches make up for this deficiency by having the 

 front part of the digestive tube in the form of a muscular tube 

 which can be turned inside out and used for boring into prey, 

 from which the juices are then extracted by the pumping action 

 ■of the pharynx. Many of these forms are parasitic upon fishes, 

 both marine and freshwater, while others, such as the freshwater 

 genus Clepsine, live upon molluscs and other invertebrates. 



SIPHON-WORMS (Gephyrea) 



Passing by the phyla including the much-specialized worms 

 known as Moss-Polypes (Polyzoa), Lamp-Shells (Brachiopoda), 

 and Wheel Animalcules (Rotifera), of which the average mem- 

 bers can scarcely be called carnivorous, though they feed to a 

 great extent upon animal matter, we come to the equally peculiar 

 phylum of Siphon- Worms {Gephyrea). This is a very hetero- 

 geneous assemblage of animals which, though they have lost 

 external traces of segmentation, are usually regarded as being 

 descended from ancestral forms of the nature of segmented worms. 

 They are exclusively marine, and many of them, as the common 

 Siphon-Worm {Sipunculus nudus), swallow sand for the purpose 

 •of extracting the nutritious organic matter which it contains. 

 One of the included groups, however, which may perhaps be 

 called the Bristly Siphon- Worms {Echiuroidea), embraces at least 

 some carnivorous species, though, as in so many other cases where 

 the habits of animals are concerned, there has been a dearth of 

 observation. None of the species are familiar except to the pro- 

 fessional zoologist, and as one consequence of this it is necessary 

 to use the scientific names in speaking about them. The bodies 

 of these creatures are plump-looking and more or less cylindrical, 

 while it is usual to find a certain number of bristles imbedded 

 in the skin which have been compared to the similar but more 

 numerous structures found in bristle -worms. A remarkable 

 peculiarity is found in the presence of a narrow, very extensible 



