201 
Cytology of Polytihagus Euglenae . 
Fig. 45. Portion of sporangium in which there were 64 spores just separated, 16 of which 
are shown in the drawing. Each spore contains a well-marked nucleus and granular cytoplasm. 
Fig. 46. Part of sporangium showing segregation of spores. Each spore-origin contains 
a nucleus and oil-drop, around which are to be seen deeply stained chromidial masses. The 
delicate lines of demarcation between the zoospores are visible. 
Fig. 47. Portion of sporangium showing fully formed spores. 
Fig. 48. Zoospore, showing oil-drop at base of cilium and near it the nucleus ; both oil-drop 
and nucleus are surrounded on all sides by the deeply stained chromidial mass. (Obj. 2 mm., oc, 8, 
freehand sketch.) 
Figs. 49-53. Five stages in the germination of a zoospore after it had come to rest. Fig. 49 
was drawn at 9.30 a.m., Fig. 50 at 10.30 a.m., Fig. 51 at 11.40 a.m., and Fig. 53 at 12.25 p.m. 
(Obj. Zeiss D, oc. 4, freehand sketches.) 
Fig. 54. Young vegetative cell, showing pseudopodia which appear to be continuous with the 
cell body and with the deeply stained chromidial mass surrounding the nucleus. (Obj. 2 mm., oc. 8, 
freehand sketch.) 
Fig- 55- Vegetative cell showing the granular chromidial network with included oil globules 
surrounding the nucleus. 
Fig. 56. Freehand sketch, showing how the haustoria of Polyphagus penetrate the cell of 
Euglena and branch in all directions. The cell is full of paramylum grains. The preparation was 
made by staining alcoholic specimens in iodine solution. 
Fig. 57. Young zygote. Male nucleus just passing into it ; female nucleus ready to enter ; 
copulating tube very short. 
Fig. 58. Zygote and female cell. The male nucleus is already in the zygote. The large nucleus 
of female cell is surrounded by a deeply stained' chromidial mass. 
Fig. 59. Female nucleus just in the act of passing into the zygote. The nucleolus is elongate 
and constricted, showing how plastic it is. 
Fig. 60. The female nucleus has just arrived in the zygote, and is in close contact with the male 
nucleus, which is much the smaller of the two. 
Fig. 61. The zygote with the two sexual nuclei in close contact. The male nucleus gradually 
increases in size, probably at the expense of material brought in from the female cell. Deeply 
stained chromidia are scattered here and there in the cytoplasm. 
Fig. 62. Sexual nuclei equal in size, and separated to opposite sides of the zygote. 
Figs. 63-66. Four stages, showing the extrusion of chromidia from the zygote nuclei. The 
nuclei become smaller as the chromatin is extruded. 
Fig. 67. Zygote showing the two small generative nuclei and the two chromidial masses. 
PLATE XIX. 
Fig. 68. The chromidial masses are fusing together. 
Fig. 69. Fusion of the chromidia complete. This large central mass, which is so conspicuous 
in mature zygotes, may be distinguished as the chromidiocentrum or the chromidiosphere. 
Fig. 70. Shows the two nuclei embedded in the chromidiosphere. The chromatin mass in each 
nucleus shows about ten granules (chromosomes ?). 
Fig. 71. The two nuclei at the periphery of the chromidiosphere. 
Fig. 72. The two nuclei slightly embedded in the chromidiosphere. 
Fig. 73* Chromidiosphere irregular in shape, nuclei embedded in it. Stage probably just after 
fusion. 
Fig. 74* The chromidia begin to lose their staining capacity just previous to germination. 
Fig- 75* Germination of zygote ; the two sexual nuclei just about to pass into the sporangium. 
Fig. 76. The two sexual nuclei just in the act of passing into the sporangium. One nucleus 
already in the sporangium, the other elongate and constricted, just passing through the narrow 
aperture. 
Fig* 77* The two sexual nuclei in the young sporangium. 
Fig. 78. Slightly later stage. 
tig. 79. Still later stage ; the nuclei are very close together, probably fusing. 
