SOME PROBLEMS OF REPRODUCTION. 37 
nucleus occur as follows:—The first differentiates an Apical 
(N1a) and a Basal nucleus (N‘b) respectively. Each of these 
again divides to form a pair of nuclei nearly superposed, which 
we term and letter Apical (N?a), Subapical (N*sa), Subbasal 
(N’sb), and Basal (N*b) respectively. Each of these four 
again divides to form a pair of nuclei of the degree N*. The 
Apical pair (N%a + Na) and Basal pair (N*b + N*b) are col- 
lateral; the Subapical and Subbasal pairs are superposed to 
form a file of four nuclei, which we name and letter Upper 
and Lower Subapical (N*usa + N®lsa), and Upper and Lower 
Subbasal (N®usb + N®lsb) respectively. Of the cytoplasm 
lining the cell-wall and surrounding the immense central 
vacuole, each nucleus attracts a certain portion so as to form 
a naked “ free cell’? somewhat ill-defined, and indeed any- 
thing but free. The following schema pas 4) shows the for- 
Synergids 
N%a N3a : Egg apparatus. 
ee ae | 
1 : Oosphere 
Ne N*usa 
ins Niaaten| 
Nélsa 
Endosperm 
N Z nucleus. 
N®usb 
sae rt 
fev i Nilsb 
l ' Antipodal 
N*b — | : cells. 
NSb a Neb 
Fic. 4.—Schema of afvisiowia 3 in embryo-sac; the vertical lines separate 
successive stages. 
