invertebratp: zoology. ltd 



dissection consists of separating the different parts b.y cutting and teasing the 

 almost invisible connecting bands, and is best done by the forceps and the 

 sharp needle (the little spear-pointed instrument). The lens maj' be turned on 

 or off according to desire, and the microscope stage makes a good rest for the 

 little dissecting pan. Look first for the alimentary canal, a greenish or 

 brownish tul)e running through the median axis of the body. It is divided 

 into the following parts : Buccal or mouth cavity. This lies in the head and 

 is not seen in this dissection. It is merely the little cavity within and between 

 the mandibles. It is easily distinguished by its very dark brown walls. 

 Oesophagus, a narrow tube running straight upwards to the apex of the head. 

 There it makes a turn toward the neck. After passing the neck, the canal 

 suddenly swells oiit into a huge crop, tapering at both ends and filled gener- 

 ally with a dark brown fluid, which consists of the food mixed with some of 

 the digestive juices. This is the ••molasses" which is disgorged to inspire 

 fear in its enemies. At the base of the crop the canal is re-inforced by 

 six finger-like exjiansions. whidi possess both anterior and posterior por- 

 tions. These are the gastric diverticula. They are hollow and thus reinforce 

 the general digestive surface. They empty into a portion of the canal which 

 forms the boundary between the crop and the stomach. It is called the pro- 

 ventriculus, and is developed in the cricket and others, into a little spherical 

 bag containing six hard, chitinous teeth. The stomach or ventriculus, is that 

 portion of the canal which extends from the diverticula to the i^lace where 

 the canal is joined by cot;ntless little tubes appearing in a sort of tangle. 

 They are the urinary or Malpighian tubules, which absorb excretory material 

 from the body cavity in which they lie. and pour it into the lower portion of 

 the canal. Hom' many separate bunches are there ':' The remainder of the 

 canal is termed the inlestine, and maj' be divided into three portions, the 

 ileum, or tapering conical portion, the colon, of small size, and slightly coiled, 

 and the rectum, with six rectal glands. 



The plate above the anus is termed the anal plate. Which is it? Draw the 

 canal and its parts, putting in the outlines of the body. Remove the en- 

 tire alimentar}^ canal, cutting it through at its two ends, and place in a watch 

 crystal. Examine then tlie floor of the thorax for whitish masses something 

 in the form of bunches of grapes. These are the salivary glands, which form 

 anteriorly two tubes or ducts, opening into the mouth. 



Return now to tlie alimentary canal ; ciit it open with the scissors, rinse 

 out the contents and examine the inner walls. The crop is marked bj" ridges, 

 which are surmounted by tiny teeth, pointing backward, to prevent regurgi- 

 tation of the solid food. (cf. later directions for mounting this.) Does the 



