EMERITA, CHLORIDELLA 181 



CHLORIDELLA 



Compare the animal carefully with the lobster, noting all 

 of the important differences. The posterior three thoracic 

 segments are free. The male possesses a copulatory organ 

 on the basal joint of the last thoracic leg. In the female 

 the opening of the oviducts is in the midventral line, on the 

 next to the last thoracic segment. Examine the chelae and 

 compare them with the chelae of a lobster. Are they ho- 

 mologous appendages in the two animals? If you have liv- 

 ing specimens, study their movements while they are walking 

 and swimming. 



A drawing of a side or ventral view will be profitable. 



Internal Anatomy. — 1. Remove the top of the carapace 

 and abdomen. Beneath the muscles note the elongated, white 

 tube, the heart, which extends from the stomach to the fifth 

 abdominal segment. The anterior end is slightly enlarged 

 and gives rise to the anterior aorta. The posterior end gives 

 rise to a posterior aorta. Note lateral arteries and ostia. 

 Remove the heart. 



2. Beneath the heart, in the male, is a whitish, pigmented, 

 flattened mass which consists of two convoluted tubes, the 

 testes. Cut this mass across between the second and third 

 abdominal segments and force it posteriorly. The two testes 

 are continuous posteriorly. Follow them anteriorly and find 

 the slender, dense, coiled vasa deferentia passing outward 

 and downward at the posterior end of the third thoracic seg- 

 ment. Cut them and lay them back where they can be dis- 

 sected later. The testes extend forward to the region of the 

 stomach. Remove the testes. 



3. Beneath the heart, in the female, are the two ovaries. 

 Trace them forward and backward, and find the very slender 

 oviduct that extends from each outward and downward in 

 the region of the antepenultimate thoracic segment. Remove 

 the ovaries, deferring the tracing of the oviduct. 



4. Beneath the reproductive organs is the granular liver. 

 This consists of two lobes which extend from the stomach to 



