912 SUilMARY OF CURRENT RESEARCHES RELATING TO 



pro'Tess, as is ordinarily supposed, from before backward, but first 

 aflccts the mcdiau or thoracic primitive segment. 



It is clearly difficult to explain the tetranierism of the segmented 

 primitive stage by the trimcrism of the terminal stage, but it is clear 

 that it must have some relation to certain stages of segmentation in tho 

 ancestor of the Insect, though none to any such fow-jointed Arthropod 

 form as, for example, the NaupJius. 



Germinal Layers of Meloe.*— Dr. J. Nusbaum gives a preliminary 

 occount of part of his researches on the embryology of the Meloidaj, 

 He discusses tho establishment of the germinal layers in Meloe pro- 

 scarahseus, which appears to be exceedingly well suited for such 

 investigations. 



The segmentation nucleus divides into two, these into many 

 vacuolated cells, which are scattered in the yolk and connected by fino 

 anastomosing processes. Some of the cells remain in the yolk to form 

 the so-called°yolk-cells, others approach the surface and form a layer of 

 blastoderm. On the third day the ventral plate and rudiment of the 

 amnion are apparent ; the former becomes segmented and the appendages 

 become marked out; along with the development of the amnion tho 

 ventral groove becomes distinct, progressing from behind forwards, 

 representing as in other insects the gastrula invagination. 



From the disguised invagination a solid strand of primary endo- 

 dcrm or endo-mesoderm results. This exhibits by the 7th-8th day 

 a special posterior mass of cells, which on tho 9th-10th day minglo 

 with the yolk-cells, but have nothing to do with the mesenteron. The 

 primary endoderm is differentiated into two large, paired, lateral, solid 

 portions, and a smaller median part. In the lateral rudiments a narrow 

 lumen appears in segmental fashion. The outer wall represents somato- 

 pleure, but the inner forms not only the muscular, but the epithelial 

 layer of the mid-gut. The central, unpaired, and inconspicuous portion 

 serves merely to unite the paired endodermic rudiments of the mid-gut, 

 except at the anterior end where it forms by broadening the greater 

 part of the epithelial wall. In the yolk, which exhibits a sort of 

 segmentation, the " yolk-cells " long persist, but are finally absorbed. 



Nutrient Food-Material of Bees-t — Herr A. von Planta has made 

 an examination of the food provided by the " nurses " for the larvae of 

 bees; he iiuds that for qiieens 69*38 per cent., for drones 72-75 per 

 cent., and for workers 71*63 per cent, is water. The chemical com- 

 position of the remaining solids is shown in the accompanying table : — 



Queens. 



Nitrogenous materials . . 45 • 14 



Fatty „ .. 13-55 



Glucose 20-39 



Ashes 4-06 



As the food varies in composition the author is inclined to reject the 

 theory that wo have here to do with a secretion analogous to that of 

 milk, and to support the theory of Scbonfeld that the food comes from 



* Biol. Ccntralbl., viii. (18S8) pp. 449-52. 



t Notice by E. Bourquelot in Arch. Zool. Expe'r. et Gen., vi. (1888) pp. xiii.-xvi. 

 See Zcitsc-lir. f. Phys. Chcmie, xii. p. 327. 



