49 



Review. — Take a specimen that has been slit on the 

 dorsal surface and make a preparation similar to the one just 

 studied except that it is opened on the back. Review the 

 work on internal anatomy indicated above excepting those 

 parts referring to the nervous system, which will be con- 

 cealed by the alimentary canal in this specimen, and to the 

 circulatory system, which will be destroyed in the prepara- 

 tion of the specimen. 



Note especially the form of the reproductive organs and 

 determine if the specimen is of the same sex as the one pre- 

 viously studied. If it is not, complete the work on the re- 

 productive organs indicated above ; if it is of the same sex, 

 other specimens should be examined after the work on this 

 one is completed. 



The suspensory nerves of the alimentary canal. — Gently push 

 the intestine to one side and note the two fine threads extending caudad 

 from the small intestine. Trace out the connection of these threads or 

 nerves with the nervous system. Note the fine branches of these nerves 

 that extend to the caudal part of the intestine. 



Make a diagram representing a side view of that part of the alimentary 

 canal caudad of the proventriculus, the last three ganglia of the nervous 

 system, and the nerves just described. 



The ventral diaphragm. — Cut the alimentary canal in 

 two between the- ventriculus and the first bend in the intes- 

 tine. Remove that part of the alimentary canal caudad of 

 this point. Cut the tracheae of one side extending to the 

 remaining part of the alimentary canal, so that it can be 

 pushed away to the other side. Be careful not to injure this 

 part of the alimentary canal till after the vagus nerve has 

 been studied, as indicated in a later paragraph. Empty the 

 wqter from the dish containing the specimen and put a few 

 drops of hcematoxylin solution on the muscles and nerves in 

 the abdomen ; after one or two minutes, wash off the stain, 

 and cover the specimen with clear water ; observe tiie ven- 



