CHAPTER 13 



THE ANIMAL NERVOUS SYSTEM 



Since the nervous system of the earthworm resembles, on the 

 one hand, that of the hydra, and, on the other, that of higher 

 animals, comparisons may now be made between the structure and 



ant. cyt. f. \ a. c.f. 



■mot 



>f. c. It- e. g. 



a. c. 



u. c. 



M, C. -..-\-8 



a. f. p. 

 



Fig. 153. — Neuromotor mechanism of Euploies patella, one of the Infusoria. 



A, diagram of an individual showing position of cut through the right margin which 

 results in paralysis of the anal cirri. B, an anal cirrus which has become detached from its 

 fiber plate and rotated on its axis 90 degrees to the left. C, diagram of the neuromotor 

 apparatus. 



a.c, anal cirrus; a. c.f., anal cirrus fiber; a.f.p., anal fiber plate; anl. cyt. f. and mh/., 

 membranelle fiber; 6. p., basal plate; c.v., contractile vacuole; e.u , ectoplasmic granules; 

 f.c, frontal cirri; mac, macronucleus; tn.c, marginal cirri; mf., membranelle fiber; m.f.p., 

 membranelle fiber ijlate; inic, micronucleus; mot., motorium; o.l., oral lip; ph , cyto- 

 pharynx; v.c, ventral cirri. (After Taylor, Univ. of California Publications in Zoology, 

 Vol. 19, 1920. 



functions of this system in representative animals. In the study 

 of irritability in the frog and hydra and of related phenomena in 

 protozoa, it has been pointed out that behavior is conditioned by 



