Branch Arthropoda 57 



pair directly in front of the antennae are the anten- 

 nules, serving the same function as the antennae and 

 probably that of smell. Each also contains in its 

 basal part an organ of equilibration. 

 h. The jointless stalks protruding from either side of 

 the rostrum are the eye-stalks, tipped with the 

 eyes. Examine them to learn the field of vision pos- 

 sessed by the lobster. 

 VII. — Breathing Apparatus. With strong scissors remove 

 one side of the carapace. The light-colored, many- 

 lobed organs thus exposed are the gills, or breathing 

 apparatus of the lobster. They are bathed in the water 

 that flows under the overhanging carapace. Move the 

 legs back and forth, and see the relation between the 

 legs and gills. Move the maxilla to which the gill- 

 scoop is attached, and observe how a stream of water 

 may thus be made to pass under the carapace. The 

 blood passes through the gills, thus coming into very 

 close contact with the water, to which it gives up its 

 carbonic acid and from which it receives its oxygen. 

 VIII.— External Openings. Find the mouth, tightly cov- 

 ered by the mandibles and maxillae. On the ventral 

 side of the telson, find a short longitudinal slit, the anal 

 opening. Examine the basal segments of the third and 

 fifth legs, to find the small external openings of the 

 reproductive organs. Those of the female will be 

 found in the basal segments of the third pair, and those 

 of the male in the basal segments of the fifth pair. But 

 one kind of reproductive organs will be found in an 

 individual. Compare this with the case of the earth- 

 worm. On the basal segment of each of the antennae 

 find a single small opening, the outlet of the excretory 

 organs. On the upper surface of the basal segment 



