44 Elementary Zoology. 



From the ventricle spring a number of arteries, which are 

 delicate and transparent, and not readily visible until they are 

 injected with some colourdd fluid. In the middle line in front 

 is the ophthalmic artery, which runs in a straight course to the 

 eyes. On either side of this is an antennary artery. Each of 

 these supplies the antennae, antennules, and the green gland 

 of its own side. A little further back there springs from the 

 ventricle on either side an hepatic artery, which, as its name 

 implies, goes to the Uver. The stomach is provided with 

 blood from the antennary artery. From the posterior margin 



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Fig. 22 — Diagrams to illustrate tiie formation of the "pericardial sac" of Arthropods 

 from the fusion of veins with originally separate openings. (After Lankester.} 



of the ventricle arise two arteries ; one of these, called the 

 superior abdominal artery, runs straight along the surface of 

 the intestine, giving branches to' it and to the adjacent muscles ; 

 the other descends obliquely downwards, and is known as the 

 sternal artery. It passes between two of the thoracic nerve 

 ganglia, and divides immediately into a forwardly running and a 

 backwardly running artery. These give off a regular series of 

 branches, which between them supply the appendages and the 

 ventral musculature of the body. The veins of the crayfish 

 are largely sinuses, i.e. more or less wide and irregularly shaped 

 channels. The blood in these enters a particularly large sinus 

 lying on the ventral side of the body ; and from this the blood 

 passes by a series of veins to the gills, and thence by another 

 series to the heart. The blood of the crayfish is a colourless 



