allee] small crustaceans 77 



Figure 5. — Eubranchipus. the Fairy Shrimp. (After Packard.) X 2. 



whitish, semi-transparent crustacean about an inch to an inch 

 and a lialf long. It is distinguished from Palaemonetes by the 

 absence of the carapace, by the presence of eleven pairs of flat- 

 tened leaf-like appendages, and by the entire absence of the more 

 usual crustacean appendages such as Palaemonetes possess. 

 Eubranchipus swims about on its back and the waving appen- 

 dages are one of the first things about it to attract attention. 

 These leaf-like legs of the fairy shrimp are used primarily for 

 breathing purposes. 



Eubranchipus is found only in the spring of the year in small 

 summer-dry pools or in ponds that recede greatly in the summer. 

 In order to hatch, the eggs have first to be dried and then frozen. 

 It is supposed these processes break the outer covering of the 

 egg and thus permit entrance of sufficient air and water for 

 growth to start. These fairy shrimps may be found in any of the 

 rather extensive summer-dry ponds or ditches. 



Fairy shrimps are positive to light of ordinary intensities, but 

 in spite of this they are found nearer the bottom of ponds in the 

 day than at night. This is because under the influence of light 

 they are positive to gravity while in darkness they are negative to 

 the same gravity stimulus. This reaction may be proven by 

 covering the eyes with shellac and lamp black, upon which treat- 

 ment the animals swim near the top, although if untreated they 

 would be near the bottom of the container. These animals are 

 more active in light than in shadow as may be seen hv placing 

 an animal in a glass dish in sunlight and cutting ofif the sun's 

 rays from time to time with an opaque object. 



Eubranchipus may be easily kept in running tap water or in 

 standing water that is not allowed to become suddenly warm. 

 The temperature should be kept within four or five degrees of 

 that in which the animals were collected. 



