NUCLEAR VOLUME AND LIFE-CYCLE OF HYDATINA 299 



into various shapes by the surrounding cells and organs. The 

 staining reaction of the full-grown oocytes also differs from the 

 younger ones, the sections of the oocytes during the period of 

 'divisional growth' of the nucelus being decidedly pink, the 

 younger stages blue. 



Of the sections passing through the nucleus of a given oocyte, 

 the first and last of the series were rejected. Since each nucleus 

 was usually cut three or four times, only one or two drawings 

 were obtained from each. Other precautions necessary in the 

 case of oocytes are discussed in a later section in relation to the 

 results obtained. 



Stomach-intestine. The wall of the stomach-intestine is com- 

 posed of a single layer of cells, polygonal in form, flattened, and 

 set edge to edge. It therefore makes a difference which way the 

 sections are cut. The Kemplasmarelation shown in tangential 

 sections is much smaller than in transverse sections. To have used 

 both kinds of sections would have introduced a great variability 

 which would undoubtedly have increased the probable error of 

 the mean, notwithstanding the larger total number of cells that 

 could have been used in that way. Only transverse sections, 

 therefore, were used. Either transverse or longitudinal sections 

 of the stomach-intestine were used, since in either case the cells 

 were cut transversely. Inasmuch as the diameters of the cells 

 parallel, respectively, to the long axis and the transverse axes 

 of the stomach-intestine are about equal, it made no difference 

 whether the organ was cut longitudinally or crosswise. The 

 gradual change, in the series of sections, from transverse to 

 tangential sections of the cells could be detected partly by the 

 shape of the sections, but better by the increasing indefiniteness of 

 the cell boundaries, or by the position of the section in the series. 

 Only those with clear boundaries were dra\Mi. Care was taken 

 to use only sections passing near the middle of the nucleus. 



The drawings of the cells of the stomach-intestine were made 

 with a camera lucida, and then enlarged photographically for 

 measurement. 



Yolk gland. The yolk gland is a syncytium in the form of a 

 thick saucer or a baseball catcher's mitt. Inasmuch as the organ 



