168 



COLLEGE ZOOLOGY 



Phylum 

 Brochiopoda 



Phylum 



Gastrotricha 



Chaefonoius 



Phylum 

 Echinodera 

 Echinoderes dujardinl 



Bristtes 



Brain 



Mouth 



Ventral 

 ganglion 



fin- 



V 



Phylum 



Phoronidea 



PAoronis 



Oviduct 

 Ovary 



Intestine 



Female genital 



pore 



Anus 



Testis 



Male genita 

 pore 



Phylum 



Mesozoa 



R/jopofuro 



Phylum 

 Chaetognatha 

 Sagitfa hexaplera 



Figure 89. Phylum Brachiopoda. Ventral view of the shell (one-half natural size). Phylum 

 Mesozoa; Rhopalura, a parasite of the brittle star. Phylum Gastrotricha; Chaetonotus, a free- 

 living species. Phylum Phoronidea; Phoronis, removed from its tube. Phylum Echinodera; Echino- 

 deres dujardini, a marine species. Phylum Chaetognatha; Sagitta hexaptera, an arrow worm 

 (6 mm. in length). 



is a straight tube leading to an anus near 

 the posterior end of the body. The excretory 

 organs are a pair of coiled tubes with a 

 flame cell at the inner end of each. The 

 eggs are very large. There is no larval stage. 

 About 200 species of Gastrotricha are 

 known. Chaetonotus (Fig. 89) is a typical 

 gastrotrich. 



mals of sedentary habit, that live in tubes. 

 The larva, called an actinotrocha, is free- 

 swimming and resembles a trochophore. The 

 adults are unsegmented, coelomate, and 

 hermaphroditic. They possess a horseshoe- 

 shaped lophophore, U-shaped digestive tract, 

 two ciliated nephridia, and a vascular sys- 

 tem which contains red blood corpuscles. 



PHYLUM PHORONIDEA 



Most of the species in this group, about 15 

 in all, belong to the genus Phoronis (Fig. 

 89). They are small, wormlike, marine ani- 



PHYLUM KINORHYNCHA 

 (ECHINODERA) 



The Echinodera are very small marine 

 worms that range from 0.18 to 1 mm. in 



