134 BULLETIN OF THE 



the short axis (Fig. 12), and much more frequently are placed ohliqtiely, 

 as in cell a, Figure 14. We would suppose that, in the event of division 

 of an elongated cell with nuclei lying transversely, the cell wall would 

 pass longitudinally between the nuclei ; but I have not been able to find 

 evidence of longitudinal divisions. From the large number of cells with 

 nuclei lying obliquely, one would infer that oblique division of the cell 

 often took place. I am unable to discover, however, that such is the 

 case ; and it seems extremely probable that the divisional plane of the 

 cell does not always coincide with that of the nucleus. 



I have found about 25 cells of the serosa with three nuclei. This 

 seems to be a matter of individual variation in the make-up of the 

 membrane, for all but three of the triuucleate cells were in membranes 

 from the brood of a single scorpion, and membranes from some broods 

 appear to have none. I have in one instance found a group of tri- 

 nucleate cells (Fig. 14, i, 2, 3, 4). At this spot nuclear multiplica- 

 tion has outstripped cell multiplication. It is nearly always easy to see 

 which of the two original nuclei has divided, for we find two of the 

 nuclei smaller than the third, and nearer to each other than to the 

 latter. In cell 2, for instance, the pair of nuclei on the left have arisen 

 from a nucleus occupying a position about midway between them. The 

 same statement would doubtless hold true for the two nuclei on the right 

 in cell 3, and here the odd nucleus is elongated. When the cell is long 

 and the nuclei all lie in the longitudinal axis, as is the case in cell J 

 it is usually impossible to determine which of the two original nuclei 

 has divided ; for the nuclei are equidistant, and nearly alike in size. 

 Another type of equidistant nuclei is shown in cell 4, — a distribution 

 quite as characteristic of very large, broad cells as the linear arrange- 

 ment is of elongated cells. I have spoken of the division of one of the 

 two original nuclei as though it always took place after the nuclei were 

 completely separate, and had taken their positions in the cell. This 

 seems to be the usual method, for I have several times found one of 

 the original nuclei in the act of dividing. But it is possible, of course, 

 for them to arise by a tripartite division, in which the three nuclei 

 would be formed simultaneously. I have found only one instance of 

 a true triple division, represented in Figures 29 and 30, and as this 

 occurred in a serosa which had plainly \mdergone degeneration, I do 

 not consider it as altogether normal. It will be noticed that the origi- 

 nal nucleus became trilobed, and that the lobes became daughter nuclei 

 of approximately equal size by the formation of three divisional planes, 

 meeting at the centre of the original nucleus. The daughter nuclei on 



