March, 1908.] On the Cytology of Synchytrium. 279 



chances of securing favorable sections of both the daughter nuclei 

 are rather remote. In the present case with sections 2 microns 

 thick, the chance is only about one in twenty-five, neglecting 

 the thickness of the nuclei though they are of about the same 

 thickness as the sections which reduces the chances very mater- 

 ially. It is evident, then, that it is not easy to get a full series of 

 nuclei in which both members of the pair show. Most of the 

 drawings therefore delineate only one nucleus. 



While centrosomes are not demonstrable on the spindles at 

 metaphase or early anaphase (fig. 1 cf. Stevens 07 figs. 18-21), 

 in what is interpreted as telophase (fig. 2) there are found enor- 

 mous asters. The manner of their appearance has not yet been 

 made out. Though usually located near the former axis of the 

 spindle they are by no means accurately placed at its poles as can 

 be seen by consulting almost any of the figures. In structure 

 also it may be seen that they vary greatly. Sometimes there is a 

 single deeply staining granule (centrosome proper) at the centre 

 of the radiations (figs. (3, 7, 8, 11); sometimes the deep staining 

 taken at the centre seems to be due simply to the convergence of 

 radiations (fig. 5). In onlv one case and that not very distinct, 

 was there seen anything approaching a clear centrosphere around 

 the central granule. But very often there is more than one 

 granule. The different granules may be located at the focus of a 

 single aster so as to look like a dividing centrosome (fig. 2). 

 They may be scattered about the focus without any very defi- 

 nite relation to the rays( fig. 8). More often the different gran- 

 ules are the centres of separate asters so that there appear two 

 centrosomes (fig. 2, 4). Rarely there may be more than two dis- 

 tinct centrosomes; figure 9 shows a case where there were three 

 connected by heavy fibrous bands of kinoplasm, while each has 

 its own aster. Figure 10 shows an anomalous condition where 

 the centrosomes are located at nearly opposite poles of the nucleus 

 while their rays meet so as to extraordinarily resemble the am- 

 phiaster common in animal mitosis. Judged by itself this nu- 

 cleus would seem to be in the prophase of division for in addition 

 to the amphiaster the chromatin is arranged similarly to the 

 spirem of the prophase. Such an interpretation seems, however, 

 entirely inadmissible, since the chromatin in prophase does not, 

 so far as is now known, assume such a spirem and the spindle, 

 being intranuclear, has no relation to an}- such amphiaster. 

 This condition was seen only in the single nucleus located in a 

 cyst where all the other asters conform to the usual type. Fig. 

 7, howe\-er, shows a condition interesting in comparison; though 

 this ma}- be simply a case where the second nucleus of a pair was 

 cut out of the section, leaving a part of its aster. Here, in addi- 

 tion to the conspicuous aster at one pole of the nucleus, is another 

 on the opposite side which though faint and lacking a ver}- definite 



