122 BY THE DEEP SEA. 



back is covered with a thick brown felt, thinner in the middle, 

 from which emerge long brown bristles and hairs of yellow 

 and green, that are also iridescent and reflect all the colours 

 of the spectrum. 



All the worms we have been considering belong to the Class 

 Annelida, the true worms, with their bodies formed of a long 

 series of rings or segments. There is another group of worms, 

 belonging to the Class Turbellaria, of much lower organization, 

 and generally spoken of as Planarians. Most of them are thin 

 textured creatures that appear capable of almost indefinite 

 expansion, and, on the other hand, they have the power of 

 contraction to a mere speck of jelly. Their voracity is in 

 inverse proportion to their size ; and the mouth is situated on 

 the middle line of the under surface, usually not far from the 

 centre of the body, and opening directly into the stomach. 

 The whole of the body is covered with very fine cilia, by whose 

 movements they appear to owe their power of gliding and 

 swimming. Some of them have a pair of tentacles, though in 

 some instances these are little more than backward folds of 

 the body, and on them or in their neighbourhood is frequently 

 gathered a cluster, or two clusters, of eye-like sensitive spots 

 which, however, do not appear to be very perfectly fitted for 

 visual purposes. In some cases the mouth is the only opening 

 to the organism, and has to serve several purposes. 



The student who would collect and study the Planarians 

 must be gifted with patience and keen sight. The fronds, 

 stems, and roots of seaweeds are suitable places to examine ; 

 also the narrowest cracks and fissures of slaty rocks, where 

 there appears to be no room even for a fine piece of tissue 

 paper. Where such rocks show a loosening of the laminae, 

 break a portion off by inserting the putty-knife and separate 

 the flakes. You will see some delicate specimens of the con- 

 ventional worm-shape, but very thin ; you will see mere specks 

 of almost transparent jelly. Lift these off the stone carefully. 

 How? Ah, that is a difficult matter, for they are so soft that 



