CAPRELLA. BRANCHIPUS. 143 



(d) How many walking legs are there? Are these all alike? 



(e) Notice the character and number of the abdominal appen- 

 dages. On the posterior surface of all but the last pair, which 

 are modified to form anal feelers, are gills. These are the only 

 respiratory organs. Why must these animals live in damp places ? 



Make a drawing of the animal from the ventral side. 



CAPRELLA. 



These animals are very common on hydroids, but because of 

 their peculiar shape and slow motions are rather inconspicuous. 

 Watch the animals and see how they move. Is the body kept 

 at rest and moved by the action of the appendages, or how is 

 movement from place to place effected? Are the appendages 

 adapted for grasping? Why are they arranged at the two ends 

 of the body? Watch specimens and see if you can determine 

 on what they feed 



The form is of interest because of its extreme modification to 

 suit it to the needs of its life. There is some difference in the 

 structure of the male and the female. The adult structure does 

 not enable us to determine the homology of appendages. 



1. Count the segments of the body. Do they differ in num- 

 ber and shape in male and female ? The first represents the head 

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

 nute protuberance at the posterior end of the body. 



2. Examine the appendages. 



(a) At the anterior end of the body are the eyes, two pairs 

 of antennce, a pair of maxillipeds, and a pair of legs. 



(b) At the hinder part of the body are three pairs of legs. 



(c) Near the middle of the body of the female, and near the 

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



(d) 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- 



