103 



(R) are tlie rostral plates, which in this stage lie widely apart, but will Mih^ci|uciitl\ 

 meet in front, to form the pseudo-rostral projection. In the interior of the 

 body, the coarsely granular. opa<|iio yolk-mass is still visible ; but it has consider- 

 ably diminished in volume, having been chiefly consumed to form the liver (1), 

 which now appears as 2 rather large sac-like organs extending backwards below 

 the yolk-mass. 



The stage represented in fig. 8 at first sight looks very different from 

 the preceding one; but in reality it immediately succeeds it. The chief difference 

 consists in the disappearance of the dorsal curvature of the body, this having been 

 changed to a pronounced ventral one, and in the consequent projection of the 

 limbs forwards instead of backwards. The embryo in this stage has very little 

 resemblance to an Isopod-embryo. whereas it agrees much more with that of a 

 decapodous Crustacean. The anterior division of the body is still broadly 

 rounded, or almost truncated in front; but its posterior (exposed) part has now 

 become distinctly segmented, the number of segments agreeing with that in the 

 adult animal. The last segment, however, is very small and still without any 

 trace of limbs. The posterior division, or tail, is about the length of the 

 anterior, and is bent in against the ventral face of the latter. It exhibits the 

 normal number of segments, which are very distinctly defined and of nearly 

 equal size, the last carrying a well-defined telson between the uropoda. At the 

 anterior extremity the eyes (0) are distinctly seen. They are still well defined 

 from each other, though in somewhat closer proximity than in the preceding stage, 

 each forming a rounded capsule, in which 3 visual elements have already devel- 

 oped (see fig. 9). The superior antennae (a 1 ) are rather large, and are extended 

 obliquely forwards, sometimes with their outer part curved more or less upwards. 

 The 3 joints of the peduncle are indicated by distinct instructions, and the flagella 

 also exhibit traces of segmentation. The inferior antennae (a 2 ) have stopped 

 in their development, being scarcely larger than in the preceding stages. The 

 mandibles (M), on the other hand, are much more fully developed and have 

 assumed their definite form and position, their upper pointed extremity being 

 articulated to the carapace at the place where the rostral plates originate. The 

 post-oral appendages are closely crowded together, and in form and mutual 

 size approach those in the adult animal, though not yet functionally developed. 

 The exopodites have wholly disappeared in the last 2 pairs, as also in the pair 

 representing the 2nd pair of maxillipeds. In the preceding pair, representing 

 the 1st pair of maxillipeds, it has considerably increased in length and extends 

 straight forwards, its outer part (br. exp.) having the form of a narrow lingui- 

 form plate. Besides this exopodal part, the epipodal part may also be traced 



