THE KMIJKYOLOGY OF EUVANESSA ANTIOPA. 97 



till finally they loose their characteristic shape and appearance and look 

 like an unarranged mass of cells. In structure there is also a regular 

 variation. At the lower end of the end-chamber upon careful examination 

 one will notice that there are three kinds of cells present in the mass 

 where at first sight they appeared to be all alike. In some the nucleus is 

 clearer and the nucleolus more distinct ; these are the css cells. Two or 

 three times as abundant and often slightly larger are the nutritive cells. 

 The epithelium cells are quite inconspicuous and often hardly so numerous 

 as the others ; they are somewhat smaller in size and the nucleoli are 

 hardly visible. 



The egg chambers are formed through the rapid multiplication of the 

 epithelial cells, forming a columar epithelium on the sides of the egg cell 

 (63: 1, ep) and enveloping with a thinner layer the adjacent nutritive 

 cells. In insects having a large number of nutritive cells quite a number 

 of epithelial cells remain in the spaces between the nutritive cells and retain 

 their primitive appearance and size. As the nutritive cells grow they do 

 not increase in numbers, at least in this insect, but attain a very large 

 size. The nucleus increases in size as rapidly as the cell does and becomes 

 irregular in outline and the contents coarsely granular. After the egg 

 chamber has attained nearly the size of the fully formed egg the nutritive 

 cells begin to decrease in size, due to the parasitic action of the egg cell, 

 and finally are reduced to a very small mass of debris. The egg cell 

 increases from the first as rapidly as the nutritive cells but the history of 

 the nucleus is quite different. This body increases greatly in size but the 

 relative proportion between it and the cell is constantly decreasing ; it 

 occupies a [)Osition on one side and near the upper end of the cell ; it is a 

 clear, transparent vesicle with a very distinct nucleolus. When the egg 

 approaches maturity and has absorbed the nutritive cells a change ensues 

 in the nucleus that is very important : first, the nucleolus becomes paler 

 and disappears ; then the outline of the nucleus become indistinct, and 

 finally no trace of nucleus is observable in the egg ; the nuclear matter has 

 diffused itself in the egg and it is a question whether part is not still 

 nucleus, though not recognizable as such. This hypothesis is the most 

 reasonable, though the spontaneous production of a nucleus under proper 

 conditions is by no means impossible, for such a process must have oc- 

 curred back in the dawn of creation when organic matter first developed 

 this structure. 



The epithelial cells vary a great deal in appearance and shape according 

 to their position. Between the chambers (63: 1, 2) they are disk-shaped, 

 showing a spindle shaped section ; on the sides of the egg cell they form 

 a regular columnar epithelium ; around the nutritive cells they make a sort 

 of epithelium but not regular as around the egg cell : at the plane where 

 the egg and nutritive cells touch, the epithelium begins to infold, forming 



