ASTACUS FLUV1ATIL18. 269 



podite (1) ; the next, small and conical, is the basipodite (2); 

 the third, cylindrical, short, and marked by an annular con- 

 striction, is the isckiopodite (3) ; next comes a long joint, 

 the meropodite (4) ; then the carpopodite (5) and propodite 

 (6) ; and, finally, the terminal d(i<-f,/l<,f odite (7). 1 



The next four somites, proceeding anteriorly, have a sim- 

 ilar general character to that which has just been described, 

 but they cease to be movable upon one another, partly by 

 reason of the calcification of the interepimeral and inter- 

 sternal membranes, partly on account of the dev. 1. pn.< nt of 

 these membranes by a foldblC inward. OT iivlition, into 

 processes, the apodemes, which project inv. ard and unite 

 with one another in the cavity of the thorax. In an Asttictis 

 which has been macerated or, better, boiled in caustic alkali 

 the floor of the thoracic cavity is seen to be divided into a 

 number of incomplete cells, or chambers, by these apodemal 

 partitions, which will be observed, on careful examination, 

 to arise partly from the intersternal, partly from the inter- 

 epimeral, membrane connecting every pair of somites. The 

 former portion of each apodeme is the endosternite, the latter 

 the endopleurite, of Milne-Edwards. As a general rule, each 

 endosternite is distinguishable into three apophyses: the 

 (irf/ir<nfial, which passes outward and unites with the de- 

 scending division of the endopleiirite to form one boundary of 

 an articular cavity fora limb; the mttppkragrfMld) \\hich is 

 directed inward, uniting with its fellow, and forming an arch 

 over the passage left in the middle line between each pair of 

 endosternites the so-called sternal canal ; lastly, the para- 

 phragmal division is a small process, which passes forward, 

 upward, and outward, and unites with the anterior division 

 of its own endopleurite, and with the posterior division of the 

 endopleiirite in front of it. 



The endopleurite likewise divides into three apophyses, 

 one descending or arthrodial, and two which pass nearly 

 hori/outally inward: the anterior horizontal apophysis unit- 

 ing with its own |>araphrairmal apophysis, the posterior with 

 the pa raphra urinal of the antecedent endosternite. The pos- 

 terior hoii/ontal apophysis, then-lore, erosses the space be- 

 tween every pair of apodemes diagonally, whence the ap- 

 pearance of a double row of longitudinal cells opening :i! 

 on each side of the sternal canal. It will be undent 



1 ProbuMy tlu- .-0X0- and basipodite together answer M th ]>: 

 the abdominal appendages, the remaining joints representing the endopodite. 



