Worms. 59 



Mcintosh remarks that the bodies of several of the elongated 

 forms resemble a semi-fluid substance that can be drawn 

 through any aperture, bent round any angle, and looped, coiled 

 or twisted in the most elaborate manner. These worms are of 

 great fragilit3^ a feature which is compensated by an equally 

 great power of regeneration. All the Nemerteans secrete much 

 mucus, and, like land snails and slugs, leave a slimy trail behind 

 them when progressing on a rock. 



The best method of collecting the smaller Nemerteans is 

 to place a number of stones overgrown with algae and zoophytes 

 in a basin of water ; after a short time a number of small 

 creatures will emerge and crawl to the water-line, among them 

 Nemerteans, small Molluscs and Annelids, and probably also 

 examples of the peculiar group of worms known as Flat Worms 

 or Planarians. These represent some of the most lowly- 

 organised forms of the animal kingdom. As in the Nemerteans, 

 the body is naked, unsegmented and without appendages, but 

 it differs in being greatly flattened, almost leaf like, and also 

 in being devoid of a posterior opening to the gut, a small aperture 

 on the lower surface serving both for the ingress of food and the 

 expulsion of undigested matter. 



The majority of British marine Flat Worms are oval in 

 outline and of small size, only a few species growdng to a length 

 of more than an inch. Leptoplana iremellaris is one of our 

 largest species ; it is sometimes found in rock-pools on the 

 under surface of stones, especially on such as are coated with 

 colonial Ascidians, Botryllus for instance, but difficult to detect 

 unless betraying itself by its movements. The colour of this 

 worm is very variable, white to grey or reddish brown, with 

 the anterior, broader end of the body marked with two little 

 groups of black dots which function as eyes. The usual method 

 of progression in Planarians is by a peculiar gliding motion, 

 but swimming can also be effected bv the flapping action of 

 the thin edges of the body. 



We will conclude this chapter on worms by referring to the 

 peculiar division known as Polyzoa, of which the Sea-mat (Flustra 

 foliacea) is an extremely common example (Fig. 74). Nothing 

 could be less worm-like than the Sea-mat ; the uninitiated 

 mistake it for a seaweed, and, as such, dried specimens are often 

 mounted in albums. If, however, one of the leaf-like fronds be 

 examined with a pocket-lens it will be seen to be made up of a 

 large number of tiny oblong cells, arranged like those of a 

 honeycomb ; each of these cells contains an animal, which 

 in spite of its size is quite highly organised, possessing a distinct 



