82 



MORPHOLOGY OF INVERTEBRATE TYPES 



parenchymatous flat worms 

 than to higher invertebrates 

 with a ccelome. 



The vacuoles contain a 

 fluid rich in albuminous sub- 

 stances. This fluid has an 

 unpleasant odor and is highly 

 poisonous to some individuals, 

 producing a strong irritation 

 of mucous membranes. 



Muscular system. Loco- 

 motion in Ascaris is accom- 

 plished by the alternating 

 contraction and relaxation of 

 the longitudinal muscle- 

 bands. When all four bands 

 have been contracted simul- 



FIG. 19. Wilsonema, a nema- 

 tode found in the soil in the United 

 States, after N. A. Cobb, from 

 Yearbook of Dept. Agriculture for 

 1914. I, lateral view of female; II, 

 dorso-ventral view of the head of 

 the same individual; III, enlarged 

 lateral view of the tail end; a, 

 ventral appendage which, together 

 with the corresponding dorsal ap- 

 pendage, acts as a sieve; b, lateral 

 tactile organ associated with the 

 sifting apparatus; c, internal ele- 

 ments (supports?) of the sieves; d, 

 inflated valvular apparatus; e, am- 

 phid; /, cuticle; g, pharynx; h, 

 nerve ring; i, excretory pore; j, 

 oesophagus; k, threefold valve of 

 the cardiac bulb; I, cardia; m, 

 wall of intestine; n, flexure of 

 anterior ovary; o, vulva; p, egg; q, 

 lumen of intestine; r, rectum; s, 

 lateral wings; t, anus; u, caudal 

 seta; v, spinneret; w, anal muscles; 

 x, apical portion of spinneret; y, 

 one of the three caudal glands. 



