214 THE entomologist's record. 



part of the egg-contents is probably absorbed by cutaneous endosmosis. 

 The trachefe are developed from the spiracles inwards, but do not 

 become visible until injected with air. Such are the broad outlines of 

 the larval development in the egg. From a tiny mass of protoplasm 

 in the yelk of the egg we get a larva produced such as we know it 

 when newly hatched. The egg-shell of most of our larger species is 

 too opaque to allow these changes to be seen, but they can be readily 

 observed in the eggs of Tortrices or Pyralides, owing to the thinness 

 of the walls of the eggs in these gToups. 



10. — On the early changes observed in the eggs of Vanessa anti- 

 OPA. — Mr. Woodworth (Butt, of New England) gives the following account 

 of these : — " The earliest stage known in the development of the egg 

 is when there are about twenty cells present. These are about uniform 

 in size, and all at (juite a distance from each other, for at this stage as 

 soon as a cell divides the resultant cells separate. This is facilitated 

 by the degenerated condition of the yelk-spherules in this region ; the 

 cells are amoeboid in shape, and the nucleus very indistinct but of con- 

 siderable size ; after dividing several times the cells arrange themselves 

 in line and commence a migTation towards the circumference. In going 

 through the degenerated yolk they sometimes leave, trailing out behind 

 them, a long j^rocess of protoj^lasm ; on reaching the edge of this region 

 they pause, gather themselves together and plunge into the mass of 

 undifferentiated yolk. While in transit, the cells divide so as to keep 

 about the same distance apart ; the}'^ do not all reach the edge at the 

 same time, but those on one side take their station long before the 

 others. On reaching the protoplasmic laj^er, the cells at once appro- 

 priate that immediately before them and so increase rapidly in size. 

 Owing to the granular material in the absorbed jDrotoplasm, the cell- 

 plasma becomes darker and the still unaltered nucleus becomes very 

 distinct. On the outside of the protoplasmic layer there was a layer of 

 greyish material ; this now forms a cap over each cell and extends 

 down each side for a considerable distance. When all these cells have 

 reached the circumference of the egg the blastoderm may be sujijiosed 

 to be fully formed, though at no time do all the cells that form it 

 resemble each other ; some commence their further development before 

 the others reach their proper position ; the blastoderm is complete aboi;t 

 twenty-four hours after dejiosition. Besides the blastoderm-cells there 

 are in the centre of the egg a large number of other cells, mostly yolk- 

 cells ; they have no definite arrangement, but are j)retty evenly distri- 

 buted over the whole egg." 



" The blastoderm-cells on one side of the egg continue to divide, so 

 that when the blastoderm is complete, the cells on one side are much 

 smaller in diameter than on the other ; they have, however, increased 

 in thickness, and so made a thicker and more compact layer ; this is the 

 beginning of the ventral j)late. The cells which make up this structure 

 are at the bottom of the egg, and extend half-way up one side. The 

 transition between this area is quite abrupt. In the farther develop- 

 ment, the ventral ]ilate sinks deejier into the yelk. This is accomplished 

 within three days after deposition. The first indication of the process, 

 is a slight infolding of tlie upper end ; the blastoderm-cells begin to 

 grow over the ventral plate from this point, and extend down the sides ; 

 the edge of the ventral plate sinks down at the same time. During this 

 process of infolding, the whole ventral plate begins an upward move- 



