210 



PSYCHE. 



[June, igo! 



be noted ; these are the Malpighian 

 tubules, the organs of excretion, four in 

 number. They arise from the alimen- 

 tary canal just back of the ventriculus 

 at a part marked by a pale transverse 

 line. Behind this line is a fourth part 

 of the alimentary canal, the small intes- 

 tine. It is of smaller caliber than the 

 ventriculus and opens into the fifth divi- 

 sion of the canal, the large intestine, 

 near the anterior end of the latter. The 

 large intestine is largest in front and 

 tapers posteriorly to the very narrow 

 rectal part. That portion of it in front of 

 the point of entrance of the small intes- 

 tine may be called the intestinal caecum. 



The salivary glands lie one on each side 

 of the oesophagus. Each is a U-shaped 

 organ with the two arms greatly dilated, 

 and the inner reaching a little farther 

 forward than the outer. The sahvary 

 duct arises from the outer lobe ; the two 

 ducts anteriorly unite beneath the oeso- 

 phagus, and the common duct thus formed 

 opens into the mouth cavity. [Without 

 removing the alimentary canal make a 

 drawing of it as seen from one side ; 

 also make a drawing of the salivary 

 glands and their ducts. ] 



[ Remove a piece of salivary duct to 

 a drop of water on a glass slide without 

 a cover glass. Examine with low objec- 

 tive of compound microscope. Notice 

 transverse lines. Press on two places 

 of the duct with dissecting needles and 

 pull gently apart a very short distance. 

 Examine again under the microscope. 

 The two parts will probably be con- 

 nected by a spiral thread ; this will be 



seen to be what formed the transverse 

 lines ; it is really a spiral thickening of 

 the walls.] 



[ Remove a small piece of fat to a 

 drop of water on a glass slide. Exam- 

 ine with low power objective. Make a 

 drawing showing the fenestrated struc- 

 ture, the definite outlines, as if the whole 

 were enclosed in a delicate transparent 

 case, and the small spherical bodies 

 — the fat cells — within. Put on a 

 cover glass and examine with the higher 

 power objective.] 



T/ie respiratory organs. Lying along 

 each side of the body is a main longi- 

 tudinal trachea (air-tube). Each arises 

 from one of the large posterior spiracles 

 and in each of the third to the ninth 

 segments forward gives off a large branch 

 to the alimentary canal and a smaller one 

 to the dorsal blood vessel (see below). 

 [Make a drawing of the tracheal system, 

 tracing the longitudinal vessels as far 

 forward as possible.] 



[Cut off a piece of one of the lateral 

 tracheae and remove it to a drop of water 

 on a glass slide under a cover glass. 

 Examine it with the lower power of the 

 compound microscope and notice the 

 tubular appearance and transverse stria- 

 tions as in the salivary duct. The spiral 

 nature of the thickening is not so easily 

 shown as in the other case but it is 

 characteristic of all insect tracheae.] 



The reprodtictive otgans. These con- 

 sist in the male of two small white oval 

 glands, the testes, lying one on each side 

 of the large intestine imbedded in the 

 muscles of the tenth segment, and of a 



