184 ZOOLOGY. 



These daintily feel about for the cause of the alarm, and, if 

 they fail to detect the proximity of an enemy, the whole 

 fascicle is cautiously pushed out, and the sentient threads 

 suddenly and confidently unfolded. 



"The polyzoon reasons from the sense of touch inherent 

 in its tentacles, and cannot be induced to exjDOse itself above 

 tlie coenoeciuni until thoroughly satisfied by these sensitive 

 feelers that no danger is to be apprehended. In fact, these 

 plant-like creatures, singly mere pouches with a stomach 

 hanging in the midst, exhibit greater nervous activity and 

 'animality,' than we find among the more highly organized 

 Ascidia, or shell-covered Brachiopoda.''' 



The epistome is a fold of the lophophore, used to close the 

 mouth and thus prevent the food from escaping from the 

 mouth. It is tongue-like and very pliable. " The border is 

 capable of a tactile motion similar to that of the human 

 tongne, and it takes cognizance of what passes into the 

 mouth by frequent and repeated jerks toward the aperture" 

 (Hyatt). It is situated immediately over the ganglionic mass, 

 and between the anus and mouth. 



The Polyzoa, as regarded by Hyatt and others, are struc- 

 turally nearly related to the Brachiopods, the higher forms 

 of which, such as Terebratula and Rhynconella, have the res- 

 l^iratory tentacles similarly j^laced around the disk or lopho- 

 phore, which is perforated at the centre by the mouth, and 

 from which the alimentary canal hangs, with a dorsal flexure 

 and anus near the mouth. " The extension of the lophophore 

 into two or three spiriform arms, the complex structure of 

 the tentacles and of the muscular and nervous systems, are 

 all more or less foreshadowed by the condition of these sys- 

 tems among the higher Polyzoa." On the other hand, the 

 Polyzoa are closely related to the worms, the Gephyrean 

 worm, Phoronis, being the connecting link. The mode of 

 development of the Polyzoa and Brachiopoda are quite simi- 

 lar, as will be seen farther on, and owing to these decided sim- 

 larities in development and anatomy, the Polyzoa and Brachi- 

 opods form a natural group or series, distinct on the one 

 hand from the Rotatoria, and on the other from the mollusks 

 and worms. 



