510 



ZOOLOGY 



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salivary glands, which 

 open close to the 

 mouth: their secretion 

 has the effect of pre- 

 venting the coagula- 

 tion of the blood taken 

 as food. 



The pharynx com- 

 municates by a very 

 small aperture with 

 the second and largest 

 division of the enteric 

 canal, the huge crop 

 (cr.), a thin-walled 

 tube extending from 

 the eighth to the 

 eighteenth segment, 

 and produced into 

 eleven pairs of lateral 

 pouches {cr. 1, cr, 11), 

 the first ten of which 

 are directed outwards 

 and correspond each 

 to a segment, while 

 the eleventh (cr. 11) 

 passes directly back- 

 wards as far as the 

 twenty - fourth seg- 

 ment. The crop is 

 capable of great dila- 

 tation, and its form 

 varies greatly accord- 

 ing to whether it is 

 empty or gorged with 

 blood. Posteriorly the 

 crop communicates by 

 a minute aperture with 

 the stomach (st.), a 

 tubular chamber with 

 a dilated anterior end, 

 and having its wall 

 produced internally 

 into a spiral fold : this 

 is the digestive portion 

 of the canal ; the blood 

 is passed into it from 

 the crop with extreme 

 slowness, and under- 



