20 



ALBERT C. JENSEN. 



is a long tube beginning just posterior to the mandibles and 

 terminating in the anterior part of the last abdominal segment. 

 It has a distinct valve at the posterior end and apparently a pair 

 of valves for each segment, Fig. i. The blood enters the heart 

 through these side ostea and is forced out through the ends of 

 the heart. The central nervous system consists of a two-lobed 

 supracesophageal ganglion in front of the oesophagus, and just 

 behind the oesophagus, between the digestive canal and the floor 

 of the body, is the subcesophageal ganglion, the first of a chain 

 that extends through the body along the ventral side. Nerve 

 fibers extend from these ganglia to the body and appendages. 



FIG. i. Last three abdominal segments, i, Heart; 2, blood corpuscles; 3, ter- 

 minal valve; 4, intestine. 



The sexes are separate in Artemia. The female is 10 to 12 

 mm. long, while the male has a length of 8 to 10 mm. Repro- 

 duction is accomplished by means of eggs that may or may not 

 be fertilized. 



In copulating the male claspers are placed around the body 

 of the female just in front of the ovisac and thus attached the 

 pair may swim about for several days, as many as five having 

 been observed. At intervals the male's abdomen may be seen 

 to bend so that the genital appendages come into contact with 

 the oviduct. Frequently copulation takes place before the ovisac 

 begins to show a brown color, due to the color of the eggs, and in 

 such cases the eggs are retained in the ovisac for as long as three 

 days after copulation has ceased. In other instances copulation 

 does not take place until the eggs are brown in the ovisac and 

 often these are deposited and even hatched while copulation is 

 still in progress. It is presumed that such a copulation is too 



