70 STARFISH GALLERY. 



pula ; a number of forms of worm-tubes, showing their great 

 variety and beauty (see especially the delicate Filograna), are to be 

 seen in the small Table-cases placed against the north wall of the 

 Gallery. Specimens preserved in spirit and illustrative diagrams 

 will make plain to the student the relation between the worm and 

 the tube it has formed. 



The Oligochceta are represented by the common Earthworm, the 

 influence of which in the formation of mould and in the general 

 ploughing of the soil has been so carefully investigated by Mr. 

 Darwin; and by the little Tubifex rivulorum (Bloodworm), which 

 owes both its red colour and its ability to dwell in mud, which is so 

 poor in oxygen as to be unfit for respiration, to the same chemical 

 compound as that which gives the red colour to our blood and 

 carries the oxygen of respiration all over the body ; the preparation 

 in the Case shows the creatures in their tubes in the mud. 



The Hirudinea, or Leeches, are distinguished from the Chato- 

 poda by the absence of bristles ; they always have a sucker at the 

 hinder end of the body, and the mode of life is always more or 

 less parasitic, though they are external, not internal ; they are 

 attached to their prey by their hinder sucker ; they are found 

 in fresh water (Piscicola), on sea-hshes (as Pontobdella), or they 

 live in moist places, as the Leech (Hirudo). The last-named has 

 three jaws, armed with as many as ninety denticles. Trochetia 

 subviridis (Land-Leech) is a species which is found rarely and 

 sporadically in England. 



The last group of Worms here represented is that of the 

 Gephyrea ; with the advance of our knowledge it is probable that 

 they will be found to be more intimately allied to the Annulata 

 than is now generally supposed. It will be seen iudeed that 

 Echiurus has bristles at its hinder end ; Sipunculus is the best 

 known representative of the unarmed Gephyrea ; Bonellia is inter- 

 esting both from the fact that it owes its green colour to a matter 

 closely resembling the chlorophyll of green plants, and from the 

 possession by the female of a proboscis, which is protruded from 

 the hole in the rock occupied by the worm ; the male is very much 

 smaller than the female, and is not nearly so well developed. 



