GENERATION OF INSECTS. 



393 



154 



shell (/) by the funis-like diiplicature {d) of the amniotic covering 

 (c), and it is protected by the two halves of the 

 egg-shell, suggestive of an analogy to the ento- 

 mostracous Cypris. The head, antenna^, and seg- 

 ments of the body are better marked ; transverse 

 depressions appear on the dorsal surface of the 

 segments, the beginning of their division into the 

 double ones of the mature insect : but the embryo 

 is still apodal, though rudiments, or buds of tho- 

 racic limbs, now begin to be discernible. Some of 

 the peripheral cells become pushed into tliese 

 buds of limbs, making them obtuse prior to elongation. On the 

 ninth day the funis is ruptured, and the alimentary canal com- 

 pleted ; but other intei*nal parts consist of cells of different sizes. 

 On the tenth day the dorsal vessel betrays itself by its pulsations ; 

 it drives the colourless blood to the head, which now becomes 

 corneous ; the antennae become clubbed, and now a simple ocellus 

 may be distinctly seen on each side. On the seventeenth day the 

 embryo leaves the debris of its shell : it presents definite segments, 

 articulated antennje, and three pairs of jointed legs ; it is, in short, a 

 hexapod larva. But at the next stage of progress it quits the high 

 road of insect development to enter a by-path of its own : new seg- 

 ments are formed from the penultimate or germinal segment; a rem- 

 nant of the funis is converted into a rudimental anal spine ; the 

 amniotic covering and the rest of the funis are moulted. 



The first spontaneous movements of the embryo ai*e to burst and 

 slip off the amnion with the first integument ; after which exertion 

 the larva reposes, with slight occasional movements of the antennae. 

 We may now distinguish {Jig. 155.) eight primary segments (1 — 8) 

 besides the anal one (9). Six new segments i5o 



have also been formed at the germinal space 

 (7/), but these are short, and collectively are 

 only equal to one of the original segments. The 

 new segments are not formed by a division of 

 the old, but by gemmation from the penulti- 

 mate segment at the germinal space. The 

 primary three pairs of legs {b a) are developed 

 from the second, third, and fifth primary seg- 

 ments. New pairs of limbs bud out from the 

 sixth and seventh segments. The female aper- 

 tures are perforated in the fourtli segment ; the male outlet is estab- 

 lished at the seventh segment, at a period when this is near the 

 posterior end of the body of the larva. It is then marked by a patch 



