MUSEUM OF COMPARATIVE ZOÖLOGY. 139 
in brief, that the object of amitotie division is the distribution of nuclear 
material throughout the cytoplasm, with corresponding increase of nu- 
clear surface. He considers it the final phase of a series of conditions 
which begins with a simple lobed nucleus, and includes branched nuclei 
of various degrees of complication. In support of this interpretation, 
Chun lays stress on the statement that cell division, after an amitotic 
division of the nucleus, has seldom or never been observed with cer- 
tainty, thereby implying that amitosis cannot have in view the multi- 
plication of cells, I do not consider this as essential to the hypothesis, 
nor, in fact, do I believe him correct on this point. The evidence of 
cell division after amitosis seems to me abundant and conclusive. It 
was observed by F. E. Schulze (75) in Amoeba polypodia; by Ranvier 
(75), Bütschli (76), Flemming (82), Arnold (787), and others, in leu- 
cocytes; by Kükenthal (85), in the lymphoid cells of Annelids ; and by 
Carnoy (’85), in various cells of Arthropods. As the foregoing shows, 
there is abundant evidence that, in the serosa of the scorpion, division 
of the cell sometimes, at least, follows amitotie division of the nucleus. 
Furthermore, the extremely regular and well ordered manner in which 
the nuclei divide, and the similarity as to size and shape of the daughter 
nuclei, seem to me decidedly against the notion that the sole object of 
the division is to disseminate nuclear substance in the cytoplasm ; for 
in those cases where amitosis is not followed by division of the cell, and 
assumably takes place simply for the purpose of dissemination, the 
nuclear products are very variable as to number, size, and shape. 
II. The Amnion. 
Plate I. Figs. 1 and 2; Plate II. Figs. 16-20. 
The amnion is much thinner than the serosa, and like it is composed 
of a single layer of flat, polygonal cells (Fig. 1, am.). But, while both 
the cells and nuclei of the serosa have become enormously larger than 
the blastodermic cells from which they originated, those of the amnion 
have changed little as regards size. The boundaries of the amniotic 
cells are not always visible, and I find that preparations, even when 
hardened and stained in the same manner, show the greatest variation 
in this respect. As a rule, the cell walls in the amnion are sharply and 
clearly defined only in preparations of membranes from advanced em- 
bryos. The same is true of the cell walls of the serosa. 
In general, the amniotic cell has but one nucleus, which usually occu- 
pies the centre of the cell. Blochmann makes the same statement as to 
