1887.] 



ON CTCLESTHERIA HISLOPI. 



47 



taneously with the antennæ and the mandibles, not the slightest 

 trace can be detected in the present stage. The extremity of the 

 head forms below in the middle a slight rounded prominence 

 (Jj), which is the first intimation of the labrum; and on the 

 opposite side of the head, close to the circular instriction, there 

 is a similar small projection (x), indicating tlie place where 

 subsequently the peculiar pivot-shaped occipital process will 

 develop. 



The next stage, represented in figs. 6 — 8 on the same plate, 

 does not seem, at first sight, to differ much from the preced- 

 ing, either in form or in size. On closer examination, however, 

 some essential changes are found to have tåken place. The outer 

 egg-membrane, or chorion (ch,) has been partly loosened, so as in 

 some embryos to obtect only a part of the body, the fluid occur- 

 ring between it and the vitelline membrane having for the greater 

 part been emptied out and retained in certain places only, where 

 it gives rise to irregular sac-like expansions of the chorion. The 

 latter exhibits a very distinct and beautiful reticular structure, not 

 observed in the earlier stages, though, in all probability, having 

 been present also in these. As to the body of the embryo, the 

 forepart, or head, is more distinctly defined, and its two pairs of 

 appendages project to a somewhat greater extent, the upper pair, 

 or antennæ (a 2 ), beeing now slightly curved, with the terminal 

 lobes more elongate, and easily recognised as the two branches 

 of the antennæ. Just in front of these appendages, on either 

 side, a very minute knob-like projection (a 1 ) has developed, 

 representing the first trace of the antennulæ. On the ventral side 

 of the trunk, eight pairs of slight transversal prominences, extend- 

 ing up the sides of the body, have made their appearance, giving 

 to the lateral contours an undulated character. These prominences 

 are the first intimation of as many legs ; and, moreover, between the 

 anterior pair of these prominences and the mandibles, a similar 

 but very much smaller prominence (fig. 8, m) is observed on every 

 side, representing the first pair of maxillæ. Finally, on each side of 

 the anterior part of the trunk an obliquely arcuate ridge (6 T ), 

 disappearing on the dorsal side, may be distinctly traced. This 



