HO Invertebrate Zoology. 



Remove the second maxillae, and expose the more rigid 

 bilobed first maxilla. The large, irregular jaws work 

 between the first maxillce and the labrum. 



Open the jaws and note the opening of the mouth. 



Make drawings of the several appendages of the head. 



The first thoracic segment, bearing the first maxillipeds, 

 has, as already noted, become fused with the head. The 

 second thoracic segment bears a pair of fair-sized second 

 maxillipeds, while the third, homologous with the third max- 

 illipeds of the lobster, bears a pair of enormous chelce. 

 Behind the chelae are five pairs of ambulatory appendages 

 supported on as many separate thoracic rings. 



Note the expanded coxal joints of the thoracic append- 

 ages, the epimeral plates. Spread the appendages apart, 

 laterally, exposing the gills. Each gill arises from the pos- 

 terior side of an appendage, near where the latter is inserted. 

 How many gills are there ? Do you find the same number 

 in the female ? In the latter do not confuse the gills with 

 the oostegites, or lamellar plates, which form the brood-pouch. 



Attached to the anterior part of the abdomen are three 

 pairs of swimming-feet, while the posterior portion bears the 

 same number of jumping-feet. Are there six separate seg- 

 ments bearing the six pairs of appendages ? Note the small 

 terminal plate. Are all the abdominal appendages biramous ? 



Digestive System. Remove the appendages from a 

 large specimen, and, after opening along the mid-ventral 

 line, pin the animal out under water or alcohol, and wash 

 any cloudiness away. 



The short oesophagus will be found to lead into a somewhat 

 rounded crop, from which extends, posteriorly, the straight 

 intestine. The hepatopancreatic cotca appear as four elongated 



