408 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



of the coalesced thoracic ganglia. Immediately beneath 

 the nerve chain the artery divides into a short and broad 

 posterior branch and a much longer and narrower anterior 

 branch. Both these branches are continuous and 

 horizontal, and are known together as the sternal artery. 



Sternal artery (PL IX, fig. 52, S.art.). This is a 

 large and well-defined median artery lying in the thorax 

 below the nerve cord and between the muscles of the 

 thoracic appendages. It is broadest at its posterior 

 portion just behind its connection with the descending 

 artery (j.d.). In front of this connection it is continued 

 forward as a much narrower vessel, from which are given 

 off arteries to each of the post-oral cephalo-thoracic 

 appendages, and also to the digestive gland. The arteries 

 supplying these appendages arise separately from the 

 sternal artery, except in the case of the last two pairs of 

 thoracic appendages. The arteries supplying these 

 appendages arise as a single vessel at each side of the 

 posterior part of the sternal artery, each of which divides 

 into two branches, each branch going to an appendage. 



The blood supply of the last five pairs of thoracic 

 appendages is very similar, and the artery supplying the 

 chela may be taken as typical of all. This artery (art.6.) 

 arises singly from the sternal artery and passes outwards. 

 A short distance from its origin it gives off a large ventral 

 branch which supplies the muscles of the coxopodite and 

 basi-ischium. The main artery passes to the extreme end 

 of the appendage, giving off various small branches to the 

 various muscles of the limb. 



Each of the arteries to the maxillipedes (art. 5), after 

 giving off its ventral branch, enters the appendage and 

 bifurcates, one branch going to the endopodite and the 

 other to the exopodite. 



The arteries supplying the first and second maxilli- 



