82 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
The results of our fresh observations upon mammals do not agree with 
those of the three last-named authors upon plants. They are, on the other 
hand, exactly in accord with and merely extend those already published by 
us in conjunction with Prof. Farmer upon the maiotic process in general (loc. 
cit.). The present detailed re-investigation of the synaptic phases in 
mammals being closely parallel with the similar observations recently pub- 
lished by us in relation to the synapsis in Triton. 
In the earliest condition in which it is possible to distinguish the cells that 
are passing into the maiotic phase, from those of the pre-maiotic layer, it is 
found that the nuclei have acquired a closer and more chromatic reticulum. 
Within each there are to be observed several chromatic centres (Fig. A). In 
many cases it is seen that the chromatic centres are double, or treble, or 
made up of even more parts of the same size (Figs. A). 
From these chromatic centres, the thread work of the nucleus radiates 
into its substance ; and it can often be seen that from each chromatic centre 
two threads wander off into the general tangle of the incipient spirem. In 
the cell represented (Fig. A) it will be seen that the number of the components 
of the chromatic centres varies from i — 5. 
In a very large proportion' of such cells, in the guinea pig, it is, however, 
found that the number of chromatic centres is 8, and that each is made up of 
two parts. This gives to the centres an appearance of duality which is un- 
doubtedly that referred to by Strasburger and his pupils. 
Shortly after the stage just described the chromatic network, or fine 
spirem, contracts into the well known synaptic figure represented in (Fig. B) ; 
and this contraction seems to be brought about by the chromatin centres 
migrating to one side of the nucleus as is seen in the figure. 
In both this and the earlier stage the whole of the nuclear threadwork is 
seen to be centred upon the chromatin bodies, and these become massed 
together in the manner represented in (Fig. C). In (Figs. B and C) the spirem 
is seen to be also gradually unwinding ; or opening out, into the characteristic 
loops shown in (Figs. C and D). 
Now through the later stages it is not difficult to persistently follow these 
loops until we see them finally each become individually converted into one of 
the synaptic gemini (heterotype chromosomes) ; and since the number of 
gemini in the guinea pig is sixteen, it follows, there being usually 8 chromatic 
centres, that these latter each represent the ends of a couple of the sixteen 
loops. 
Their frequently double appearance is due in the first place to the fact 
that at this stage they tend to be aggregatecTin '-•airs : although subsequently 
they become all dissociated, and even the ends of the loops deviate in the 
coarse spirem figure as we shall see. (Figs. D, E, F.) 
It will be observed that the sequence of events is at this period by no 
means simple, and the phases of the synapsis so far as we have now gone 
may be conviently elucidated by a diagram, wherein only two double and one 
triple chromatin centres and their associated loops are drawn. (See next 
page.) 
* Moore and Embleton. On the Synapsis in Amphibia. Pro. Roy. Soc, 1905. 
