FLAT- WORMS. 



47i 



The accompanying illustration shows one of these worms (Stenostomum 

 monocelis) in process of giving rise to a second individual. In the upper half of 

 the figure (0) is the mouth, and (s) the auditory 

 organ of the parent; the coiled tube (v) being 

 part of its excretory apparatus, and (e) some 

 eggs. In the lower half (o) is the mouth, and 

 (s) the auditory organ of the newly-forming 

 individual. The division may begin successively 

 at several places on the body before the last and 

 oldest bud is attached, so that it results in the 

 formation of a chain of segments lying one 

 behind the other. 



Suborder Dendrocoela. 



The members of this division differ from 

 the preceding in having the intestinal canal 

 tree-like, or divided into a number of branches. 

 The mouth, which is situated on the inner 

 surface, leads into a muscular and flexible 

 pharynx, capable of protrusion like a proboscis. 

 The body is broad and flattened, usually broader 

 in front than behind, and generally bears a pair 

 of eyes upon what may be termed the head. 

 In the genus Polycelis — the species of which 

 occur in meadows and stagnant water — there 

 are a large number of eyes, the broad front end of 

 the body being bordered with from thirty to 

 fifty of these organs. On the other hand, 

 Geoplana subterranea, which lives in sandy and 

 clayey soil, in company with earth-worms, upon 

 which it feeds, is entirely devoid of organs of 

 sight. Many members of the group are in- 

 habitants of the land and fresh water, and are 

 collectively termed Planarians. These are often 

 objects of considerable beauty, being both 

 graceful in movement and decked with various 

 colours. The two-striped Geodesmus bilineatus, 

 for instance — which has been found in hothouses 

 in Europe, where it has been doubtless intro- 

 duced from the tropics with exotic plants — is a 

 dull yellowish colour above, but is ornamented 

 with two reddish brown bands, extending on 

 each side of the back, and meeting near the 

 front and hinder end of the body. Another planarian not infrequently introduced 

 into the conservatories of Europe belongs to the genus Bipalium, this species 



SINGLE-EYED TURBELLARIAN, StenOStOmum 



(much enlarged). 



