350 



ESSENTIALS OF ZOOLOGY 



by the muscular pharynx. In the pharynx it receives the secretions 

 from the pharyngeal glands and is then passed on through the 

 esophagus, where it receives the secretions from the calciferous glands. 

 It is then passed into the crop and is stored there long enough for 

 the secretions of the calciferous glands to neutralize the organic acids 

 which may be present in the food. It is then passed into the gizzard, 

 where it is ground by contractions of the muscular walls of that organ. 

 This process is aided by sand grains which are swallowed along with 

 the food. From the gizzard the food is passed into the intestine 

 where digestion is completed and the absorption of digested mate- 

 rials is accomplished. 



Circulatory System 



The blood of the earthworm consists of a liquid plasma in which 

 there are numerous colorless cells. The red color of the blood, as 

 seen in a living specimen, is due to a pigment known as hemoglobin 



Beart 



:^-Dorsal vessel 



Intestlno-tegumeatai7 

 - — vessel 

 .-Ventral vessel 



Sub-neural vessel 



Septa 

 Dorsal vessel 



Septa j^ 



Intestino-tegumentary 

 vessel 



VIII 

 Dorsal vessel 



CEsopbagus 



Ventral vessel 



6ub-neural vessel B 



Efferent Intestinal vessel 



Nephridium 

 Lateral-neural vessel 



D 



Ventral 

 vessel 



Sub-neural vessel 



Afferent intestinal vessel 



Dorsal vessel 

 Typblosolar vessel 



Ventral vessel 

 Sub-neural vessel 



Parietal vessel 



Fig. 129. — Circulatory system of the earthworm. A, Longitudinal view of vessels 

 in somites VIII, IX, and X : B, transverse section of the same region ; C, longitudinal 

 view of the intestinal region; D, transverse section of the same region. (From 

 Hegner, College Zoology, The Macmillan Company, after Bourne, after Benham.) 



