508 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Endophragmal Skeleton (PL III). 



The Endophragmal Skeleton (figs. 17 and 18) is a 

 complicated system of calcined plates in the thorax, 

 which serves chiefly as an attachment for muscles, but 

 also as a sujDporting framework for the viscera. It is 

 formed by the inturning of the edges of the epimera and 

 sternum of each segment. Typically two vertical plates 

 arise from the fore and hind border of every thoracic 

 sternum, and a similar plate projects from both edges of 

 the pleuron at the side. Thus each plate is double, as 

 it is duplicated throughout by the neighbouring 

 segments. The outgrowths from the sterna are known as 

 the endosternites, those from the pleura (or epimeral 

 plates) as the endopleurites. The endophragmal 

 skeleton in E. bernhardus is not well developed and 

 differs in many respects from that typical of the 

 Macrura. The endosternites are only fully developed in 

 the fifth and sixth thoracic somites. The endopleurites 

 conform more nearly to those of such a type as the 

 Crayfish. A sternal canal is never present. Median 

 plates caused by the folding of the sterna sagitto- 

 longitudinally are developed on the fifth and sixth 

 thoracic segments. 



Preparations of the endophragmal skeleton, from 

 which the form of the individual somites may be studied; 

 can be best made in the following way. 



Remove all of the carapace behind the cervical 

 groove, separating it carefully from the underlying 

 epimera. Cut off the abdomen at the peduncle, and each 

 limb a few joints from the proximal end. Clean out the 

 gut and stomach, after cutting a window in the cephalic 

 shield, and such portions of the overlying muscle, etc., as 

 can be scraped away without injuring the skeleton, and 

 boil gently for a short time in a 10 per cent, solution of 



