298 Trans, Acad. Sci. of St, Louis. 



80 that I doabt if such a change occurs in these forms in any 

 case. 



The nucleus of the egg in its early stages shows the ordi- 

 nary spherical form with one or two large nucleoli and 

 abundant sharply stained chromatin. As the egg nears 

 maturity, the chromatin becomes indistinct with the ordinary 

 stain, the regular contour of the nucleus disappears, and the 

 only prominent feature remaining is the large nucleolus. 

 The nucleolus itself shows commonly an irregular form and 

 appears vacuolated. Careful staining and examination en- 

 ables one still to see a nuclear network upon which fine 

 granules are distributed. These granules stain blue with 

 gentian violet. This distinct staining reaction and the marked 

 difference between these and the cytoplasmic granules outside 

 justify the claim that this material is chromatin, which is only 

 in a very finely divided state. Such networks can be seen in 

 figures 4, 5, 6, 7 and 8, where the necessity of distinguishing 

 chromatin from cytoplasm by a difference in shade in the draw- 

 ing has made the nuclear network more prominent than it 

 really appears in the microscope. The difficulty of showing 

 the presence of chromatin in the unfertilized egg led Zacha- 

 rias, in 1887, to say that no chromatin framework had been 

 demonstrated in the egg of Pteris serrulata, Marchantia poly- 

 morpha^ Pirius sylvestrisy Thujopsis dolohrata, Lilium candi- 

 dum, Monotropa hypopitys^ov among animals in Unio or Rana. 

 The same difficulty has recently been noted by Gardiner in 

 Polychaerus caudatus. Chromatin is easily stainable in the 

 last division spindle in the formation of any one of these eggs. 

 It may be readily demonstrated in the younger stages of the 

 egg itself, but in the ripe egg Zacharias could find no satis- 

 factory micro- chemical evidence of its presence at the time 

 of fertilization, although a plastic framework could be found. 

 These observations seem to show that at the time just preced- 

 ing fertilization the egg chromatin differs so greatly in its 

 distribution at least, if there is no change in its chemical char- 

 acter, that it fails to give the ordinary reactions which so 

 easily demonstrate its presence before and after this period. 

 During the entire time the nucleoli maintain their size and 

 position unchanged. 



