410 M. E. Hesse on the Pranizse and Ancei. 



styles which issue between the parts of the apex of the rostrum, 

 and are probably employed in producing wounds from which 

 the blood may flow. Behind the footjaws the lower part of 

 the head exhibits a deep, longitudinal median fissure, which 

 completes the mouth, and forms at its extremity a commissure 

 destined to facilitate the introduction of fluids by suction. Below 

 the mouth, in some individuals, there is a very prominent biiobed 

 sac, forming a sort of crop, the office of which is unknown, 

 although it appeared to contain food : its presence is the more 

 remarkable as it occurs but rarely, and disappears when the 

 Crustacean becomes converted into an Anceus. 



The thorax, generally of an ovoid form, is equally convex above 

 and below, and is covered with a transparent skin. It presents 

 no well-marked segments, except the first and second, and 

 sometimes the third, which are very distinct. The third segment 

 is rarely entire; it is often indicated by two lateral pieces, 

 different in substance from the skin upon which they are fixed, 

 and which appear to be rudiments of the carapace. To these 

 lateral pieces are united others, resembling the elytra of the 

 Meloes and Hemiptera. Analogous pieces are also placed at 

 the base of the other thoracic limbs, to which they serve as 

 points of attachment; and, lastly, these are sometimes united by 

 a sort of ridge, forming a narrow margin to this part of the 

 body. The middle of the thorax, both above and below, presents 

 vertical and transverse lines forming four divisions, of which the 

 angles are truncated at the centre by a small lozenge-shaped 

 piece; these lines probably indicate the part at which the skin 

 is divided when the animals undergo their last transformation. 



The legs present no peculiarities requiring notice, with the 

 exce])tion of the first two, which are fixed on each side to the 

 base of the head, the apex of which they scarcely pass ; they are 

 armed with strong claws, which enable their possessor to adhere 

 firmly to any object. These legs, which constitute the first 

 pair of thoracic members, makes the number of these twelve 

 instead of ten, as has hitherto been supposed ; but they are 

 wanting in the Ancei. 



Structure of the male Ancei. 



In the transformation of the Praniza into Ancei, the only 

 parts which undergo no metamorphosis are the antennae, the 

 thoracic feet, and the abdomen. The head, on the contrary, 

 shows the most extraordinary changes ; from being very small, 

 it acquires a volume at least equal to that of the thorax. From 

 above, the head of the male Anceus is seen to be armed in front 

 with two large moveable laminae, generally falciform and denti- 

 culated on their inner margin, and elevated at the apex, so as to 



