106 Dr. F. Miiller on the Metamorphoses of the Prawns. 



feet (fig. 2), the outlines of the future upper jaw may be dis- 

 tinctly recognized ; the living contents are more or less com- 

 pletely withdrawn from the posterior ramus ; the anterior ramus 

 is still pretty well filled, but we may already see that it will be 

 destitute of bristles after the change of skin. Of these feet, 

 therefore, besides the stem which becomes converted into the 

 upper jaw, only a short bristleless stump will remain. (An organ 

 of this kind, rendered very striking by its dark brownish colour, 

 was in fact observed once [on the 3rd of January] in a very 

 young Zoea; but even this soon disappears completely). Be- 

 tween the origins of the anterior feet two ganglia of considerable 

 size, contiguous in the median line, may now be distinguished. 

 In the anterior angle between these two ganglia the eye is situ- 

 ated, siirrounded by numerous small orange-coloured globules 

 (oil-drops?). Over the eye, and concealing it from above, a 

 turbid finely granular tissue has been formed ; from each side 

 of this springs a small transparent button, projecting in a hemi- 

 spherical form beyond the frontal margin. The intestine, liver, 

 and heart are already present, of the same form as in the younger 

 Zo'ea. 



It is probable, as shown by their bristles being already indi- 

 cated, that at the next moulting the rudimentary feet become 

 effective, and the Nauplius becomes converted into a Zoea, to 

 the appendages of which the names in use for those of the ma- 

 ture animal may be applied with less wresting of their meaning. 

 I therefore henceforward indicate the first two pairs of feet of 

 the Nauplius as antennae, and the third as upper jaws ; and of 

 the four new pairs the two anterior as lower jaws, and the hinder 

 as footjaws. 



In the Zoea-iorva. (figs. 3-7) our larva was observed from 0*8 

 to 1'6 mill, in length. During this life-period the two eyes are 

 developed, ten or eleven new segments are formed, with a pair 

 of feet on the first, and rudiments of feet on the five following 

 rings, and, lastly, the lateral caudal appendages are produced. 

 These new parts are of course met with in very variable form ; 

 in other respects the animals undergo no important changes, 

 even in size; for their increase in length proceeds almost ex- 

 clusively from the gradual extension of the eleven new seg- 

 ments. 



The carapace, 04 to 0-5 mill, long, is at first almost circular 

 and flat, but it soon bends downwards and covers laterally the 

 parts of the mouth and the basal joints of the feet. Posteriorly 

 it exhibits a shallow sinuosity where it lies over the body. 

 Whilst, at its first appearance, it separates from the body behind 

 what are now the upper jaws, the separation is now eflfected be- 

 hind the second pair of footjaws, and the carapace projects 



