EUGYKA. 



67 



surface, together with the transverse or primary vessels, 

 which are rather conspicuous, a coarse reticulation, the 

 square meshes of which are each occupied by a conical 

 eminence (fig. 48). On account of the prominence of 

 the longitudinal bands, these eminences, which look 



FIG. 48. Two of the cones of the branchial sac of Eitgyra arenosa, seen in 

 front. Highly magnified . (Alder, in Ann. Nat, Hist. (3) XI, pi. vii, f . 4. ) 



like so many miniature bee-hives (fig. 40) seem to be 

 arranged in six or seven longitudinal series, though 

 they perhaps really compose transverse series between 

 the primary vessels. 



FIG. 49. A small portion of the branchial sac of Eugyra arenosa, showing 

 the cones in profile. Highly magnified. (Alder, in 'Ann. Nat. Hist.' 

 (3), XI, pi. vii, f. 3.) 



Each conical eminence is formed of a double spiral 

 coil of secondary vessels united at the apex, so that the 

 blood will pass up one coil and down the other. The 

 coils are perfect, and the stomata, which are co-extensive 

 with them, appear to be scarcely, if at all, interrupted 



