DEYELOPMENT OF THE OVABIES IN THE BLOWELT. 419 



germinal chamber {Keimfacli). He was followed by Prof. Huxley 

 (10, 11), Sir John Lubbock (19), Claus (8), and others. Stem 

 enunciated the view that the function of the terminal chamber is 

 the formation of germ-yelks ; but he does not regard all the cells 

 in the chamber as germ-yelks. Sir John Lubbock went a step 

 further and wrote as follows : — " In their earliest stage, the egg- 

 cell and the vitelligenous cells cannot be distinguished from each 

 other, and no one, I think, who has carefully examined the upper 

 part of the egg-tube in any Hemipterous or Dipterous insect can 

 fail to be of the same opinion." 



I agree entirely with Sir John Lubbock in this, that all the 

 cells in the terminal chamber are alike ; but when he concludes, 

 " The egg-tube contains, indeed, at this end, cells which are 

 neither vitelligenous nor egg-cells, but which are capable of 

 becoming, under certain circumstances, either one or the other," 

 I cannot agree with him, and my reasons will appear in the sequel. 



The Egg-chamhers. — This term was first applied, I believe, by 

 Brandt (6) to that portion of the egg-tube which contains definite 

 ova. In some insects each egg is formed from a single cell ; this is 

 so in the Orthoptera ; such ova are designated by Brandt pandistic. 

 In other insects several cells are concerned in the formation of 

 the ovum ; these ova he termed merdistic. 



In the meroistic egg Brandt calls the lovvest cell the egg-cell, 

 the others he terms nutrient or yelk-cells. 



The part played by these nutrient cells is a matter upon which 

 there is great divergence of opinion. Brandt's view, which has 

 been generally adopted in text-books and widely accepted, is this: — 

 The egg-cell in the meroistic egg is the only cell enclosed by the 

 chorion, and the nutrient cells remain outside and ultimately 

 disappear. These are supposed to be in some way concerned in 

 the nutrition of the egg-cell. Tlie great increase in the size of 

 the egg-cell is due to the deposition of yelk-granules within it, 

 around its nucleus, which Brandt regards as the germinal vesicle. 

 Similar changes also occur in the panoistic egg, which only differs 

 from the meroistic in the absence of the nutrient cells. 



Weismann (20) maintains, on the other hand, that all the cells, 

 the nutrient as well as the egg-cell, are enclosed in the chorion, 

 and that they all take part in the formation of the yelk, ultimately 

 fusing into a single mass ; and this, as I shall show hereafter, agrees 

 with my own observations. 



With regard to the import of Brandt's egg-cell there is less 



