3O Invertebrate Zoology. 



The Digestive System. The mouth leads through a 

 short (esophagus into a thin-walled stomach, the five lobes of 

 which normally lie in the cavities of the five arms, though 

 certain lobes, and indeed at times, while feeding, the entire 

 stomach, may be completely everted through the mouth. 

 Do you find the gastric retractors, bands of muscle which 

 draw the lobes of the stomach into the cavities of the arms ? 

 The lobulated digestive glands appear in each ray as a pair 

 of voluminous masses of a light olive-color. Each gland 

 unites with its fellow, centripetally, and opens, through a 

 common pore, into the stomach. Note the suspending 

 mes enteric fold. 



Inflate the stomach by blowing into the oral opening. 

 The organ will be found to lead, above, into a short cone- 

 shaped intestine, which opens to the exterior through a 

 minute pore, the anus. Leading from the left wall of the 

 intestine is a somewhat branched organ, the respiratory 

 tree. It is made up of two main divisions, separated by 

 an interradius. The organ may perform an excretory 

 function. 



The Reproductive System. - Though the testes and 

 ovaries bear a superficial resemblance to each other, the 

 sexes are separate. The sexual glands appear in mature 

 specimens as a pair of light-colored, grape-like masses, 

 extending from near the body out into each ray. 1 Trace 

 the ducts to their external openings. (The openings may 

 be found well into the angles between the arms.) 



Draw the reproductive system. 



1 The testes are in living specimens of a whitish color, while the 

 ovaries are pale yellow. 



