20 G. 0. Sårs. 



Inner organs. 



Though the body in alcoholic specimens is rather 

 opaque, it is not difficult, by suitable preparation, to render 

 it sufficiently pellucid to trace some of the inner organs 

 rather distinctly. The musculature especially is easily observ- 

 able, both the strong dorsal and ventral muscles acting 

 upon the body itself, and the muscles joining the several 

 appendages (see figs. 1, 2, 3). 



The eye, as is generally the case in preserved speci- 

 mens, is less easy to observe, because the pigment very 

 soon becomes dissolved by the action of the alcohol; but, 

 as far as I can see, it does not seem to differ in structure 

 from that in the genus Diaptom,us. Of cuticular lenses no 

 trace is present. ^) 



The alimentary canal may be faintly traced, especially 

 in the lateral view of the animal, extending through the 

 anterior division of the body somewhat ventrally, and forming 

 a considerable dilatation in front. On entering the tail, it 

 contracts to a narrow duct, passing about through the axis 

 of that part, and debouching at the end of the last segment 

 somewhat dorsally. 



The heart occupies its usual place, lying dorsally at the 

 limit between the first 2 pedigerous segments. 



The ovaries in some of the specimens are pretty con- 

 spicuous (see figs. 1 and 2), and of exactly same structure 

 as in the genus Diaptomus This is also the case with the 

 testes in male specimens, and it not happens infrequently, 



^) In a large fresh-water Diaptomid from North America 

 (probably Diaptomus shoshone of Forbes) I have found 2 such very 

 distinct lenses dorsally, much as in the marine Pontellidæ. 



