HARDWICKE'S SCIENCE-GOSSIP. 



243 



Analysis of the Kieselgiihr of Hanover, by M. 

 Tiegler (1862) :— 



Silica 84-15 



Alumina i'4° 



Ferric oxide °'7° 



Manganese traces. 



Calcic carbonate i'75 



Carbonate of Magnesia i'io 



Potash 0-25 



Water 10-40 



Losses o - 2s 



ioo'oo 



Analysis of the Kieselgiihr of Franzenbad, by 

 Rob. Hoffmann (1863) :— 



Silica 77-000 



Alkalies 0-401 



Magnesia 0049 



Lime traces. 



Oxides of Iron and Alumina . . . o'o,io 



Phosphoric acid 0T90 



Water 6'ooo 



Losses (in part organic) i5'45° 



ioo'coo 



Analysis of a Kieselgiihr of Holland, by L. Lossier, 

 (Geneva, 1878) :— 



Silica 84-37 



Phosphates of Iron and Alumina . . 2-55 



Lime 0-35 



Magnesia 0-07 



Alkalies o'6o 



Water and Organic matters .... i2'68 



IOO"62 



( To be continued.) 



THE EGGS OF CHRYSOMELA POLITA. 



THESE eggs, which are laid in irregular masses 

 of about thirty loosely stuck together by a 

 glutinous matter which soon becomes hard and 

 brittle, are about i'8 mm. in length, and somewhat 

 over '5 mm. wide, elliptical, with narrower pointed 

 ends. They vary very much in colour, from pale 

 straw-yellow or buff, to a bright salmon-rose, or 

 even orange-red. They have a thick outer shell 

 which is very finely and regularly pitted, but is 

 often cracked, and has the appearance of scaling off. 

 I was first struck by the thickness, hardness, and 

 brittleness of this shell, giving it a curious resemblance 

 to the calcareous shell of the bird's egg. I soon 

 found that it might be easily removed by rolling the 

 eggs under the camel's-hair brush in a little water, 

 without injury to the inner or vitelline investment 

 and without prejudice to the future development of 

 the eggs, provided they were kept in a sufficiently 

 moist atmosphere — a condition which is easily realised 

 by placing them on a fresh leaf with a few drops of 

 water in a shallow saucer covered with glass. 



This double investment of the insect egg, is not 

 always so easily demonstrated. Herold (" Unter- 

 suchungen liber die Bildungsgeschichte der wirbel- 

 losen Thiere im Eie "), in the preliminary remarks to 



lines of which is J 

 too inch 



the description of the figures on plate xiii., details 

 the method adopted by him for removing the outer 

 shell of the egg of Musca vomitoria in order the better 

 to observe the changes taking place in the contents 

 during the development of the embryo. The process 

 consisted in fixing the eggs to a gummed surface or a 

 wet wafer, and, when dry, by gentle pressure on the 

 side, bursting off the outer shell held fast in the gum 

 or wafer, and turning out the egg with its inner 

 investment entire. 



Under the microscope the pits in the outer shell of 

 the polita egg are seen to be irregularly polygonal 

 or roundish, of unequal sizes, the largest being 

 about ^(55 inch in diameter, dark by transmitted 

 light, and separated by a much finer, clear network 

 of irregularly hexagonal meshes, the width of the 

 to \ that of the cells — say 

 In April last I obtained a few eggs of 

 Chrysomela fastuosa, which I find described in my 

 notes as ' ' very elongate — white, and beautifully 

 shagreened ; about i§ mm. in length by J mm. 

 broad ; somewhat pointed at the ends." I am not 

 able to find any note of it, but the impression on 

 my memory is that the " shagreening," under the 

 microscope, was a very fine and delicate hexagonal 

 reticulation, reminding me at the time of the like 

 appearance in the polita egg. The egg of Apis 

 mellifica has a similar hexagonal reticulation. Von 

 Liebold, in " Wahre Parthenogenesis" (page 105), 

 quoting Leuckart, says, "As in the eggs of most 

 insects, we distinguish also in that of the bee, two 

 membranes, an inner, the so-called vitelline mem- 

 brane, and an outer, the egg-shell or chorion .... The 

 former is structureless, whilst the latter .... is overlaid 

 with a delicate hexagonal moulding (Leistenwerke), 

 as with basket-work (einem Geflechte)." This recalls 

 the sculpturing of many lepidopterous eggs, and the 

 comparison of the same to flasks enclosed in wicker- 

 work. How this sculpturing is impressed upon the 

 insect egg is that which puzzled me for a long time, 

 but which seems to be explained by reference to 

 the genesis of the outer shell or chorion itself. I 

 quote the account of this structure from Von Liebold 

 ("Beitr'age zur Parthenogenesis"). At page 57, he 

 says, "The inner surface of this ovary-tube proper 

 \tunica propria of Leydig] appears beset in various 

 places with a fj'/iWtv-epithelium composed of nucle- 

 ated cells." Then, at page 61: "This epithelium 

 separates itself later from the tunica propria of the 

 ovary-tube, and forms itself into the chorion surround- 

 ing the egg," &c. The chorion then, or outer shell 

 of the egg, in these cases is composed of a layer of 

 cylindrical cells, whose long axes are vertical to the 

 surface of the egg, and which by mutual pressure 

 will naturally assume a prismatic columnar shape, 

 giving to the surface the appearance of polygonal 

 reticulation. 



J. A. Osborne, M.D. 

 Milford, Letterkenny. 



M 2 



