still inore rudinentary than, the proventricular fold in the mos- 

 quito and probably has a similar function. The importance of 

 this fold in the trypanosome infection of Ciilex makes its pi^es- 

 ence in ticks of concern in connection with spirochete infection. 



Alimentary sac and its diverticula . These organs, when fresh- 

 ly distended with blood, form smooth, dark red, lobulated masses. 

 As the araoxint of blood diminishes, the diverticula become almost 

 black in color and exhibit innumerable small lobulations. 



In the young, vmengorged tick, the long, narrow diverticula 

 show active pulsatile movements that probably have no effect in 

 drawing blood from the host but serve to distribute fluid to dif- 

 ferent parts of the sac. 



From the entrance of the esophagus and extending posteriad 

 to the neighborhood of the rectum there is a large central reser- 

 voir. This reservoir extends anteriorly a little beyond the 

 entrance of the esophagus so that this latter is situated upon 

 the ventral surface of the sac. From the ventral surface poste- 

 riorly a conical tag passes ventrally behind the spermatheca to- 

 wards the rectum. The basal part of this tag contains blood, but 

 as it narrows it becomes a clear tube of capillary character. 

 This portion of the canal appears functionally inactive and can 

 play no part in the passage of matter from the sac to the rectum. 

 In 0. savignyi , therefore, the alimentary system is practically 

 a closed one ^"^^^ ^^ 2* "p^^^'*^^- ^^ is entirely closed; there is 

 no passage between the "small intestine and the rectal ampulla 

 (Enigk and Grittner 1952 J>J7. 



From the central reservoir a number of blind diverticula 

 originate, the disposition and extent of which are constant in 

 all ticks. There is an anterior, a lateral, and a posterior series. 

 The anterior series, found only in Ornithodoros , is absent in Rhi pi - 

 ce phalus and Hyalomma . It consists of a single, small median dL. 

 verticulum extending ajiteriorly so as to lie over the gene's organ. 

 The three pairs of lateral diverticula arise together at about the 

 level of the entrance of the esophagus. The anterior lateral di- 

 verticulum is short, the median one is somewhat longer, aiid the 

 posterior one is large and long. The anterior and middle branches 

 divide into two or usually three blind pouches. The posterior 



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