15 



It is also worth while to examine the gills and body- 

 cavities of Crustacea (crabs, &c.), for larval Nematodes 

 and Trematodes, and the various cavities of shell-fish 

 for larval Trematodes, and their empty shells for 

 Nemertines, &c. 

 (6) Free-living forms in the water 

 or on shore. 



Nemer- 



15) are 



generally 



between 



dredged in 



The Nemer- 



Planarians and 

 tines (see Fig. 

 numerous, being 

 found under stones 

 tide-marks or 

 shallow water. 



tines are often in tangled 

 masses. Empty shells should 

 be examined for them, and also 

 sea-weeds. Some Nemertines 

 make gelatinous tubes, or even 

 liurrows in the mud. Pelagic 

 Nemertines, swimming freely 

 at the surface, are very rare. 



Free-living Nematodes are 

 known in the sea, but many 

 more no doul)t remain to be 

 discovered. 



A single Nematomorph, 

 Nectonema, has sometimes been 

 caught by the tow-net swim- 

 ming at the surface. 



PoLYCH^TA (see Figs. 8, 9, 

 and 16, and p. 7) are very 

 abundant. Unless dredging 

 operations can be carried out, 

 they are best obtained by shore- 

 collecting at low tide. The 

 burrowing kinds often betrtiy 

 their presence by leaving 

 " casts " of sand which has 

 passed through the alimentary 

 canal on the surface of the 

 ground, and may be obtained 

 by digging in such spots. 



Gephyrea (see Fig. 10) will, as a rule, only be 

 obtained by dredging, but a few may be foimd between 

 tide-marks, burying themselves in mud, or forming tubes, 

 or tubular excavations in soft rock. Some live as " com- 

 mensals " with corals or sea-urchins, or in empty shells. 



Figure 15. 



\ Ncinortine, Eiiiiemertcs ijracilin, 



■nlargt'd, in a rhanictcristic- 



illy twisted position. [NemeR- 



TINEA.] 



