106 BINUCLEATE CELLS IN TISSUE CULTURES. 



Fici. 18. Late telophase. Tlie two dauKlitor oells are seen, separated and spread out tliiuly; pro(i)pla.siii stains niucli 

 more lightly; nuclei well defined and contain eoarselj' granular chromatin. In each daughter nucleus 

 the beginning of a nucleolus is to be seen; but is very small compared with the size" of this body at 

 maturity. X 1,012. 



Fia. 19. Late prophase of mitosis, in cell probably of conncctive-ti.ssue type; two centrospheres at opposite poles; 

 nuclear membrane has disappeared; s])ireme well marked; mitochondria .sliort and thick. \o. 42, 

 Lewis (see fig. 1). Figures 20 and 21 are from the same preparation. X 1,0.32. 



Flo. 20. Early prophase in a nucleus showing beginning ilirect unilateral fi.ssion; skein forming, nucleoli tlisappearing; 

 centrosphere .still single, situ.ated in the fi.ssure; mitochondria becoming .shorter and tliicker, and are 

 intermediate in these respects between those seen in figure 8 and those of figures 19 and 21 ; nuclear mem- 

 brare has ahnost disappeared. Cell of connective-tissue type. X 1,032. 



Fin. 21 Late prophase in a nucleus umlergoing direct unilateral fi.ssion. Skein has formed and nuclear membrane luis 

 disappeared; one centrosphere is to be seen in the cleft, and there is some indication of a second on the 

 opposite siile of the nucleus, in ti)C area devoid of mitochondria. X 1,032. 



Fig. 22. Prophase in a binucleatc cell. Early stage. Skein is forming; membrane and imcleoli are di.sappearing. 

 Some clu-oniatin has become segregated in the area of contact between the two parts. The method of 

 fi.\ation and staining does not permit of the centrosphere and mitochondria being seen. No. 14 Lewis 

 (see fig. 2). X 1,012. 



Fio. 23. Prophiise in a binucleatc cell of connective-tissue type; somewhat later stage than figure 22. In each nuclear 

 portion there has been forme<l simultaneously a skein and the nuclear nicMibraiio has disappeared. The 

 chromatin material of the combined double nucleus will form a single equatorial plate of chromo.somes, 

 as in figure 67. Only one centrosphere, containing two centrosomes, is seen in the prejiaration, situated 

 at one extremity of the fusing iniclous, it having come from the interval between the nuclear parts. It is 

 thus probable tliat the s|5indlc will form i^arallcl with tlie long axis of the fusing nucleus. Mitochondria 

 are short and thick. No. 18, 21:2; 14, Lewis. 7-day chick heart, grown for 2 days in Locke (0.25 per 

 cent dextrose); osmic-acid vapor and iron hematoxylin. X 1,032. 



Plate III. 



Figs. 24-35. A series of drawings from a living connective-tissue cell made at 15-minute intervals for 2J hours. The 

 nucleus at the start was elongated and notched at one side. It was seen to take various forms, and 

 ended as two separate nuclear parts. The .series thus shows direct nuclear fi.ssion. It will be seen that 

 the centrosphere is contained within the unilateral cleft, and when the imcleus ultimately divides the 

 centrosphere is situated between the parts of the nucleus; mitochondria stream across the interval 

 separating these two parts. Tlie nucleolar l)0(lies undergo interesting changes. The imclear outlines, 

 position of nucleoli and centrosphere, the cell outlines, and princijjal features of the cytoplasm were 

 sketched in freehand from direct oKservation of the living cell. The drawings were afterwards retoucheil 

 by reference to fixed preparations. Small circles represent fat globules, and short tlireads mitochondria, 

 r, figure 24, marks the centrosphere. .5-day chick heart; .")7 hours' cultivation, from No. 7, 9 : 1 : 15, 

 in Locke (0.5 per cent dextrose) with extract of chick embryo. Xabout 900. 



Figs. 36—47. Fragmenting nuclei showing probable effect on form of imcleus of prolonged growth in unchanged media; 

 oufUnes of nuclei very irregular, each has a number of lobes; in some cases separation of these lobes has 

 taken place. Culture .shows other evidences of degeneration. No division of the c\toplasm following 

 division of the nucleus was observed. Drawn from various cells selected from No. 23, 12:1: 15 (Lewis). 

 5-<iay chick stomach in Locke (0.5 per cent dextrose) . Zenker; Mallory connective-tissue stain. Culture 

 grown for 6 days in the same media. X 1 ,012. 



Figs. 48-58. A collection of nuclei of irregular form, grown in media containing alcohol; centrospheres are sketched in 

 to show their characteristic relation.ship. Same preparation as figure 10. X 1,500. 



Fig. 59. A regular paired nucleus from the same preparation as that from which the series 48-58 was drawn. Some of 

 tlie nuclei have escaped distortion. X 1,500. 



Pl.^te IV. 



Figs. 60-70. A series of camera-lucida drawings from a single living hinucleate cell of the connective-tissue type, 

 which was observed continuously for 8 hours. At the beginning there were two separate nuclear parts, 

 with one centrosphere; the parts combined to form a single mitotic figure, and the successive stages of 

 mitosis are seen in figures 66 to 70. The ultimate result is two separate mononuclear cells, each con- 

 taining a single centrosphere. The series brings out the fact that the parts of the "double" nucleus are 

 not independent .so far as their reproductive capacity is concerned, but in cell division they combine and 

 act as a single nucleus, c, figure 60, represents the centrosphere. 7-day chick heart, grown for 19 hours 

 when the observation commenced. Locke (1 per cent dextrose) with extract of chick embryo. Culture 

 of March 1.5, 1915. XI, .500. 



