472 



WORMS. 



(B. kewense) having been first obtained in the plant houses at Kew. It is a 

 striking creature, measuring upwards of a foot in length when fully extended, and 



c 



structure of a dendroccelian (enlarged 5 times). 



having the grey colour of its skin relieved by three dark longitudinal bands running 

 along the back from the head to the tail. It is exceedingly flexible and contractile, 

 looking sometimes short and stout, and at other times long 

 and narrow. The head is susceptible of many changes of 

 form, assuming the shape of a hammer-head or the blade 

 of a cheese -cutter, and the next moment being tongue- 

 shaped. The skin is richly supplied with glands, secreting 

 a sticky slime, by means of which the Bipalium is able to 

 ascend perpendicular surfaces, and to lower itself from a 

 high point by letting out a thread of the material. It is said 

 to feed upon earth-worms, and to propagate by division ; the 

 tail-end breaking off and growing into a second individual 

 by acquiring a head, proboscis, and intestine. Land 

 planarians are abundant in the damp tropical forests of 

 Ceylon, South America, and Australia ; and a rich population 

 of allied forms frequents the sea. One of the most striking 

 of these marine forms is the tufted planarian (Thysanozoum), 

 represented in the illustration on p. 473. Here the back is 

 covered with many rows of dark-coloured tufts; the lower surface being pure 

 white, and the head end furnished with a pair of ear-shaped lappets, in which the 

 sense of touch appears to be concentrated. The creature is shown clinging to a 



SMOOTH POLYCELIS. 



a, The animal ; c, The eyes 



TWO-STRIPED GEODESMUS 



(enlarged twice). 



planarian worm, Planaria gonocephala (enlarged). 



branch of seaweed, with the head elevated so as to exhibit its lower surface, and 

 feeling for a new surface of support. Planaria gonocephala, figured above, is one 

 of the land forms. The general structure of the intestine in all the animals of this 

 group is shown in the illustration at the top of the page. 



