PHYLUM ARTHROPODA 123 



the genital opening, receiving sperm from the copulatory sac and being stuck 

 together into packets by a fluid from the cement gland. The egg guide directs 

 the eggs in their passage to the exterior. 



Draw from the side the parts of the reproductive system which you have 

 been able to find. 



d) The digestive system: The larger part of the internal cavity is filled with 

 the digestive tract. Remove the reproductive system. Clean away the fat 

 body and cut off one lateral side of the abdomen and thorax and the same side 

 of the head. Identify the short esophagus extending inward from the mouth 

 and opening into a large crop which fills most of the cavity of the thorax. Behind 

 the crop is the elongated stomach, or ventriculus, partially concealed by six thin- 

 walled gastric caecae. Each gastric caecum is attached by its middle portion 

 to the wall of the stomach so that one of its pointed ends projects forward and 

 the other backward from the point of attachment. The anterior part of the 

 stomach, covered by the caecae is distinguished as the proventriculus or gizzard, 

 but it is not well differentiated in the grasshopper. The posterior end of the 

 stomach is marked by the presence of a tangle of threads, the Matpighian 

 tubules. Beyond this region is the intestine, at first wide, then presenting a 

 short narrow portion, the colon, then widening into a rectum, which extends to 

 the anus. The rectum frequently contains a cylindrical pellet of faeces. Its 

 surface is marked off by longitudinal muscle bands into six expanded areas, 

 known as the rectal glands. The position of the anus under the suranal plate 

 has already been noted. Look in the sides of the thorax among the muscles and 

 fat body for the salivary glands, a cluster of small round glands attached to a 

 duct. The ducts open into the mouth. 



Draw an outline of the animal from the side and put in the parts of the 

 digestive tract. Other systems which the student has seen well enough may also 

 be entered upon the drawing. 



e) The excretory system: The threadlike Malpighian tubules arising at the 

 junction of the stomach and intestine are the excretory organs. They are out- 

 growths of the digestive tract and are therefore entirely distinct morphologically 

 from the excretory organs of the other animals we have studied, that is, the 

 nephridia. The insects have lost the nephridia. 



/) The nervous system: Cut through the esophagus, leaving it in place, and 

 remove the digestive tract. Look in the median ventral line of the abdomen for 

 the ventral nerve cord. How many ganglia are present in the abdomen? Trace 

 the nerve cord forward into the thorax. Note here, as in the lobster, a so-called 

 endoskeleton, really an ingrowth of the exoskeleton, extending like beams across 

 the floor of the thorax. Remove these and muscles, etc., so as to expose the 

 thoracic nerve cord. Find the three large thoracic ganglia, one in each segment 

 of the thorax. Anterior to these is the sub-esophageal ganglion. From this the 



