14 



HARDWICKE'S SCIENCE-GOSSIP. 



The surface of the chorion is more or less distinctly 

 areolatcd, especially at the anterior pole where the 

 areolae constantly compose an ornamental and rich 

 rosette around the central pit." The so-called front 

 or upper pole of the egg, or its cephalic end, is that 

 end which, lying remotest in the ovitube, is last 

 laid ; and in which the head of the future embryo 

 will be found. In eggs of an elongate shape the 

 tail of the embryo often occupies the opposite, lower, 

 or hinder, pole of the egg, the first laid end, by 

 which the &gg is sometimes attached to the leaf or 

 branch in an upright position. Describing the egg 

 "of Miisca vomitoria, Herold says (" Disquisitiones 

 de Animalium vertebris carentium in ovi forma- 

 tione ; " description of PI. xiii.) : "By reason of its 

 curved shape, four regions or surfaces may be 

 discovered in every egg. The convex surface under 

 which the venter of the maggot is developed may be 

 called the ventral rtgxon ; the opposite concave side, 

 distinguished by a slit, the dorsal region, under 

 which the dorsum of the maggot comes to lie, and 

 which at the laying of the egg has a position fully 

 parallel with the back of the fly. The two surfaces 

 lying between these regions, corresponding to the 

 two sides of the maggot, may be called the right and 

 left lateral regions. As results from the foregoing, 

 the lateral regions and the ventral region of the egg 

 correspond exactly in position with the same regions 

 in the fly at the moment when the egg is laid." In 

 the case of lepidopterous eggs however the embryo is 

 frequently doubled up in a U-shape, so that the head 

 and tail lie close together in the front end of the egg. 

 The egg of M. vomitoria is an instance of perfect 

 bilateral symmetry. It is the only radially symme- 

 trical or even spherical form of lepidopterous eggs, 

 which makes it (nearly) always impossible, as 

 Leuckart states, to distinguish between dorsum and 

 venter, and right and left sides. The egg of Rtimia 

 cratcegata, however, furnishes at least one exception 

 to this rule. 



In the end of June last I received a box containing 

 a dead female of this moth, together with about eighty 

 eggs which she had laid in it after her incarceration. 

 They were scattered about in rows of two or three 

 to eight or nine, and sometimes one row on the top 

 of another. The egg may be described as of a short 

 oval shape, truncated anteriorly (at the front pole 

 or cephalic end), and laterally compressed ; pearly 

 white, iridescent, speckled coarsely and sparsely 

 with irregular spots of a bright red. They were in 

 various stages of development when I received 

 them, and the doubled up horseshoe-magnet-shaped 

 larvae were in many plainly visible through the trans- 

 parent shell. Whether or not (at the moment of 

 laying) these eggs occupied what may be called the 

 normal position, as described above by Herold, they 

 were all now lying on their sides (right or left in- 

 differently) ; those in the same row of course having 

 their cephalic ends all in the same direction. Each 



egg was about "75 mm. long, and '5 mm. in its 

 broadest diameter (i.e. dorso-ventral). The general 

 shape closely resembles that of Sphinx ocellata as 

 figured and described by Herold (loc. cit. PI. viii. 

 fig. I, &c.), which eggs also lie on their sides. The 

 whole surface is covered with a beautiful hexagonal 

 reticulation with dotted fields and elevated boundary 

 lines, due to the juxtaposition of the cells of the outer 

 layer of the chorion. These hexagonal areolations pass 

 gradually into others of a lozenge or leaf-like shape, 

 surrounding in a double rosette a little pit in the 

 centre of the upper pole or flattened end of the egg, 

 and pomting out the situation of the micropyle.* 

 This rosette resembles closely that of Euprepia 

 (Chelonia) Caja, as figured by Leuckart (PI. iii. fig. 9), 

 with which I have also compared it. But the upper 

 pole of the Rumia egg has another structure. This is 

 an elevated angular ridge surrounding the whole polar 

 area and giving the appearance of a lid to that end of 

 the egg, especiallyjust before hatching. The opening, 

 after the caterpillar has escaped, corresponds pretty 

 accurately with the area so enclosed ; so much so 

 that until I found one eating its way through it I 

 always expected to find the burst-off operculum. 

 Leuckart describes a similar peculiarity in the egg of 

 Gastropacha neustria (p. 173 and PI. iii. fig. 5). 

 ' ' The eggs of Gastr. neustria show yet greater pecu- 

 liarities . . . especially in their external shape. In the 

 hitherto mentioned species of this genus [viz, querciis, 

 potatoria, dumeti'], the eggs are globular, or even 

 depressed in the direction of the antero-posterior axis 

 as in the case of G. dumeti ; here, however, in Gastro. 

 neustria, we have eggs of a conical form, flattened 

 in front where they are furnished with an elevated 

 border (wulstigern Rande), narrowed posteriorly 

 and laterally compressed in a marked degree." This 

 border ridge, judging by the figure, is not so sharply 

 defined in G. neustria as in R. craticgata ; but 

 Leuckart describes also an inner concentric ridge 

 (Ringwulsl) in the former which is wanting to the 

 latter egg. 



The polar area in the egg of R. cratccgata, with 

 its surrounding elevation, is ellipsoidal — rounded at 

 one end, but running out in a sharp point at the 

 other. Its longer axis corresponds with the greatest 

 width of the egg, and the pointed end runs down a 

 little on the adjacent side. This pointed end of the 

 ellipsoid indicates the position of the head, as the 

 rounded end does that of the tail, of the future larva, 

 which, when developed, lies doubled up within the 

 shell, with its dorsum external, in the manner figured 

 oiPieris hrassiccc, by Herold, in PI. xii. figs. 3, 4, and 5. 

 There is consequently complete bilateral symmetry in 

 the egg of Runiia cratccgata, and the position that 

 is to be occupied by the different parts of the future 



* If the hexagonal meshes of a net surrounding an opening 

 in it were strung upon an elastic thread, and this thread should 

 then forcibly contract so as, to close the opening, it would give 

 ,-i somewhat similar shape to the adjacent meshes. 



