DEVELOPMENT OF TK1CHOGKAMMA E-VANESCENS. 171 
The Amitotic Division in the Developing Embryo. 
It has been shown that the number of nuclei in the 
blastoderm stage becomes subsequently reduced, but that soon 
afterwards, at about the stage in PI. 11, fig. 15, amitosis can 
be found. Mitosis never occurs in the stages I have examined,, 
and I suspect that it never occurs at any stage of develop- 
ment ; but between polar bodies and blastoderm, and larva and 
pupa, I have no stages. I cannot find mitosis in the ovary 
of the imago, but my series is not satisfactory, and subse- 
quent work may cause me to alter my views. In the dividing 
nucleus the large median chromatic body may be seen to 
elongate (PI. 10, figs. 6a and 6b), while the nucleoplasmic 
zone ( NP . Z.) is unaltered in shape. The nucleoplasmic 
zone soon constricts and becomes elongate. The chromatin 
mass becomes roughly dumb bell-shaped, and the nucleus 
divides into two by a constriction (PL 10, figs. 15 a and b). 
From the scanty evidence afforded by PL 11, fig. 11, it 
seems probable there is no proper mitotic figure in the polar 
bodies. The figure draw in PI. 11, fig. 11 a, closely resembles 
the stages of amitosis in the embryonic nuclei, except for the 
absence of the nucleoplasmic zone. It is probable that mitotic 
figures will be found during and after the formation of the 
pupa. . The probable reason for the absence of mitosis during 
early development is evidently connected with the explana- 
tion of the form of the nucleus. (See the discussion, p. 26.) 
Mesoderm. 
In the section of the young larva one always finds loose 
cells in the body cavity. These I believe to be mesoderm ; 
such cells are shown in PI. 11, fig. 27, MC. ; PI. 12, 
fig. 33, MC. ; fig. 34, X. The formation of mesoderm is quite 
unaccompanied by the appearance of mesoblastic somites; 
these cells which form the mesoderm are derived from nuclei 
which sink inwards from the periphery in the stage of fig. 15, 
PI. 11, but as the disposition of such nuclei varies I find it impos- 
sible to state exactly where they arise. It will be clear, after 
