DAPHNIA 169 



with two fused thoracic segments. The abdomen forms a mi- 

 nute protuberance at the posterior end of the body. 



2. At the anterior end of the body are the eyes, two pairs of 

 antenna?, a pair of maxillipeds, and a pair of legs. 



3. At the hinder part of the body are three pairs of legs. 



4. Near the middle of the body of the female, and near the 

 anterior end in the male, is another pair of legs. 



5. On two of the segments which do not bear legs are gills. 

 If time permits, make a drawing. 



BRANCHIPUS. (Fairy Shrimp. ) 



These animals may be found in pools of fresh water in the 

 early spring, just as the ice is leaving. Their method of swim- 

 ming by means of the large, expanded appendages should be 

 observed. 



1. Into what parts does the body seem to be divided? Do 

 all of these parts show segmentation? 



2. Find the following organs, 

 (a) The stalked, prominent eyes. 



(6) The antennce. In the female the first are slender and 

 the second vestigial. In the male the first are slender and the 

 second are enormously enlarged to form a clasping organ. 



(c) The labrum forms an upper lip. 



(d) The mandibles, beneath the labrum and by the sides of 

 the mouth. Do they have cutting-edges? 



(e) Vestigial maxillce behind the mouth. 



(/) Swimming appendages. How many are there? Notice 

 the fringe of hairs on each. What are these for? Remove one 

 and examine it with a microscope. The lobes have been des- 

 cribed as exopodite and endopodite, but their exact relation- 

 ship is not certain. 



A drawing is desirable. 



DAPHNIA. 



This small fresh-water form frequently occurs in large num- 

 bers in small pools and brooks. Determine how it swims. Being 



