Life-history of Tetraclinis articulata. 595 
it practically certain that no splitting of the chromosomes had occurred at 
this time. 
In the next figure (Fig. 53) the chromosomes have become arranged 
at the equator of a multipolar spindle, but apparently no splitting has as 
yet taken place. Fig. 53 shows the daughter chromosomes approaching the 
poles of the spindle. 
It may be noted that each of these three stages (Figs. 50-3) found 
near the centre of the archegonium, a position which appears to be normal 
for Cupressoideae, having been observed by Lawson (26) in Cryptomeria 
and by Miyake (32) in Cunninghamia . In Thuja , according to Land (24), 
the division takes place below the centre, but not quite at the base. In 
Taxodium , however, Coker (9) reports that the fusion nucleus passes to the 
base of the egg before dividing. 
Figs. 54 and 66, which represent the next stage seen in Tetraclinis , 
show the two daughter nuclei one above the other at the base of the egg, 
evidently shortly after division is completed. Whether the daughter nuclei 
pass down before or after the completion of the first mitosis cannot be 
stated. The next division results in the formation of a tetrad of free nuclei 
(Figs. 55, 56, and 67), the tetrad being oriented, in different cases, in every 
conceivable manner ; it seems likely that the variation met with at this 
time may explain the still greater variation met with in the proembryo 
after walls have appeared. 
Figs. 56, 66, and 67 show how small a proportion of the egg is occupied 
by the young proembryo, and Fig. 56 also shows the ventral canal nucleus. 
It may be mentioned that in Tetraclinis the ventral canal nucleus has never 
been seen to divide after fertilization has occurred, contrary to the case of 
Thuja (Land (24)) and Juniperus (Nichols (36)), where division quite often 
occurs. The next stage seen shows a proembryo, in which walls have been 
formed, containing eight cells ; it seems probable that the walls appear, as 
is usual, in the transition from the 4-nucleate to the 8-nucleate stage, 
though a different method of wall formation has been described in Thja 
(Land (24)). No detailed drawings have been made of these later stages of 
the proembryo. That no simultaneous divisions occur after wall formation 
may be inferred from the fact that counts of the cells (including the upper 
tier of free nuclei, where such was present, which was usually not the case) 
in serial sections of fourteen walled proembryos (before they extend into 
the prothallus below the base of the archegonium) gave the following 
numbers of cells: 8, 9 (two examples), 10, 11, 12 (two examples), 
13, 15, 16 (two examples), 17, 18 (two examples). Five of the least 
irregular of these have been used as the basis of Diagrams 1 to 5 in Text- 
fig'. 5* These, however, are in each case slightly more regular than the 
originals, though the general arrangement of tiers appears to be essentially 
accurate. The number of cells (or nuclei) in each tier is indicated on the 
S s 2 
