A critical study of the cytology of Crepis virens. 
125 
eviclence afforded by Galtonia and other forms, that the parallelisms 
of tliese presynaptic prophases represent the reassociation of the two 
longitudhial halves of a univalent chromosome which separated during 
the preceding telophase. This pairing of threads is therefore to be 
regarded as the preparatory concentration of the daughter halves 
of univalent chromosomes which will separate on the homo- 
type spindle, and consequently as homologous with the con- 
centration of paired threads of somatic prophases. 
As the nucleus approaches synapsis, the chromatic contents begin 
to aggregate (fig. 105). The beads arrange themselves into niasses, into 
groups, or into squares (figs. 105, 106 and 107). The parallel arrang- 
ment of threads and beads is constantly most marked (figs. 104 and 106). 
Aggregation proceeds (fig. 107) and the chroniatin becomes increasingly 
concentrated, sometimes leaving the linin as a colourless reticulum 
(fig. 107). GraduaUy the linin contracts front the nuclear peripher)^, and 
the more or less finely beaded reticulum collects round the nucleolus 
(fig. 108). The chromatin exhibits varying degrees of concentration; 
in some nuclei it may be in the form of fine beads (fig. 108), whilst in others 
it may be collected into relatively larger rounded portions (fig. 109). 
The nuclear contents draw more and more closely together (fig. 110), 
until they are massed at one side of the nucleus in the typical beaded 
s\maptic knot. At first this Imot may be more finely granulär than that 
resulting front the definite chromatic aggregation series of prophases, 
but it would be impossible to distinguish front which mcthod the dose 
synaptic tangle, that immediately follows, had enstted. 
Between the two distinct tj’pes of presynaptic phases, there may be 
an intermediate series in which definite chromatic aggrcgations are present 
in the resting nucleus (figs. 111 and 112). These chromatic bodies elongate 
and divide into rounded beads (figs. 113 and 114) which are larger in size 
than those of the fine presynaptic phases (figs. 102 and 103), but are 
smaller and more numerous than the typical longitudinally divided chront- 
atic bodies of the coarser chromatic series. GraduaUy (figs. 115 aitd 116) 
the beads collect into synapsis (fig. 117). Such a series has been found 
in material fixed with acetic alcohol. 
Parallel cases to that of Crepis virens have been described by Gre- 
GoiRE (20) and Mottier (36) in plants, and by the Sciireixers (50) in 
animals, showing the occurrence of different types of somatic and hctero- 
type prophases due to the niethod of distribution of the chromatic contents. 
Gregoire (20) found two distinct series of presynaptic phases m the 
pollen mother-nuclei of Allmm fistulosum. The one has a fine reticulum 
