DAPHNIADiE. 69 



Gruithiiisen has published a very interesting memoir 

 upon the Baphnia sima of Miiller, in vol. xiv of the 

 * Nova acta Physico-Medica Academia? Cesarise Naturae 

 Ciiriosorum,' part i, 1828, in which he describes at some 

 length the circulation of the blood, as observed by him, in 

 this insect. He describes two hearts, arterial and venous, 

 and gives a figure, nnich magnified, of the blood in 

 motion.* His figm'e of the creature itself, hoAvever, is not 

 very correct, or it is a species different from that of Miiller. 



In M Edwards's work on the Crustacea, vol. iii, the 

 reader will find a description of almost all the species 

 known at the time of its publication, and to that we refer 

 him, as containing the fullest list of described species 

 belonging to this family. 



Anatomy and Plujsiologjj, 8fc. — The body is composed 

 of two parts, very distinct from each other : the one, much 

 smaller and projecting, forms the head ; the other, much 

 larger, and consisting of a thorax and abdomen, is con- 

 tained entirely within a very slender and delicate shell. 

 The valves of this shell are, in most of the species, per- 

 fectly smooth round their circiuuference, but on the 

 middle are marked, either with reticulations or deep 

 crossed lines, in one or two species, forming a mesh-work, 

 or, as Schoefter says, they are shagrcened like the skin of 

 a shark. They are open on the anterior margin, and 

 united to each other along the posterior edge, as far as 

 the extremity, but have no hinge, being as it were 

 simply soldered together, to use the expression of Goeze, 

 allowing the animal, however, to open and shut them to 

 a certain degree at will. In some species these valves 

 are prolonged posteriorly to a point, which, at some 

 periods of their growth, and in some varieties, is very 

 long, in others very short, and in some altogether 

 wanting. 



In the head, the covering of which is harder than the 

 other portion of the shell, we distinguish the following 



* L. c, t. xxiv, f. 6. 



