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- 



