31 6 Mottier . — The Development of the Heterotypic 
thread, or network, with a single row of chromatin granules (Fig. 19). In 
some preparations, nuclei with the structure indicated in Fig. 17, occupy 
one end of the loculus, while in the other end of the same loculus the 
structure of Fig. 20 is present, and in the middle portion complete synapsis. 
In other preparations, nearly all the nuclei in the pollen mother-cells of the 
whole anther show the structure of Figs. 19, 20, 21, i.e. from a spirem or 
network with a single row of small granules to complete synapsis. In one 
end of such an anther there may be a few cells with the structure of 
Fig. 17 ; in others there are no such nuclei, but all show the structure 
as described in the preceding sentence. In none of the preparations was 
there anything to indicate unusual or faulty fixation. 
Examining each of these conditions now in detail, it is seen that in 
Fig. 22, the chromatin masses are collecting into a mass at one side of the 
nucleus, as all conceivable stages between Figs. 17 and 23 are present 
in the same loculus. In Fig. 22, the linin threads are very beautifully 
shown, some being very delicate and staining blue or appearing colourless, 
whilst others are thicker and hold some of the safranin stain. Here and 
there two or more of these linin threads may have a parallel course, and 
some of the chromatin masses are paired, but how such phenomena can 
justify the doctrine that a double spirem is being formed is difficult to 
comprehend. There seems to be as strong evidence that a triple or 
quadruple spirem is formed, because the chromatin masses are frequently 
aggregated in clusters of three or more. In the second condition described 
above, we have a structure just preceding synapsis which differs from that 
shown in Fig. 22. Here it is certain that the chromatin becomes more 
finely reticulated, so that small and uniform granules are formed, and that 
these granules are being arranged into a single spirem (Figs. 19, 20). In 
nuclei presenting the structure of these figures, the nucleolus, or nucleolar 
material, is almost always flattened in one or two masses against the 
nuclear membrane. The chromatin thread is very frequently oriented 
with reference to the flattened nucleolus, as indicated in Fig. 20. This 
orientation gives the impression that the thread is disposed in many 
interlacing loops or turns, that extend out from the flattened nucleolus. 
There seems to be no closer connexion, however, between nucleolus and 
chromatin thread in this condition than in the other. Some preparations 
show that in the entire anther all pollen mother-cells were in some stage 
between that of Figs. 19 and 21. In Fig. 21 the synaptic condition is 
about complete. In the section from which this figure was drawn, about 
one-third of the nuclei presented the contracted mass, while in the rest 
some such condition as Figs. 19 and 20 was present. In such cells it was 
noticed that the flattened nucleolus was very constant and thereby con- 
spicuous ; but this was less so in the former condition, although it is 
frequently met with (Fig. 23). In preparations showing the structure of 
