14 Dr. F. Miiller on the Development of the Stomapoda. 



The carapace, which leaves the three hindmost thoracic seg- 

 ments uncovered, is flat, and scarcely, if at all, bent down laterally. 

 Its posterior part has nearly the form of the so-called Sea-Mouse, 

 or of a quadrangle with its corners drawn out into points 

 directed backward and forward, with its fore and hind margins 

 of equal width (about two-thirds of the length), and its sides 

 gently arched. The posterior margin is notched in the middle 

 as far as it lies upon the body. The anterior angles lie over the 

 origin of the posterior antennae ; between them the carapace is 

 produced forward, becoming rapidly narrower and running out 

 into a point, which projects beyond the body about one-sixth of 

 its length. The length of the anterior portion of the body, 

 covered by the carapace, is to that of the posterior uncovered 

 portion about as 3 : 5. 



The foremost division of the body (fig. 2), bearing the eyes 

 and antennse, which is almost entirely filled by a large nervous 

 mass, has a quadrangular form ; it is 0*28 mill, in length, and 

 the same in breadth behind; the width in front is only half as 

 much ; on the middle of its lower surface stands a short spine 

 directed forward. From its anterior angles spring the eyes, the 

 extreme convexities of which, when turned quite laterally, are 

 0"5 mill, apart ; one-third of this distance is due to the frontal 

 margin and the slender basal joints of the peduncles. The ter- 

 minal joint of the eye-stalk forms an oblique cone, the anterior 

 margin of which is about two-thirds the length of the posterior 

 margin ; the latter is about equal to the diameter of the basal 

 surface, over which the true eye arches itself. 



Below the frontal margin, in the middle of a semicircular 

 process, is seen a small black si7iffle eye, which perhaps indicates 

 that even here the development commences with monoculoid 

 forms. 



llather nearer to the eyes than to the posterior antennse, the 

 anterior antenna spring from the margin of the body ; they have 

 a three-jointed stem, a two-jointed upper branch, and a jointless 

 inner lower branch, and attain one-fifth of the length of the 

 body. Of the three joints of the stem, the intermediate one is 

 half the length of each of the other two ; the first joint is cylin- 

 drical, the third thickened at the end. The upper branch is 

 slender, as long as the stem, and bears a long bristle at the end 

 of the first and two at the end of the short second joint. The 

 inferior branch is of a pointed conical form, shorter, but far 

 thicker, than the upper, with a long terminal bristle ; about the 

 middle of its upper surface it bears six thin cylindrical filaments 



diiFer so remarkably from the preceding ones, under the special name of 

 the tail, may also be justified from the developmental history of the animal 

 under notice. 



