96 ETHEL NICHOLSON BROWNE 



are distributed through the cytoplasm, so that in the second divi- 

 sion they are arranged as in the first. They are divided again 

 en masse when the cell divides. 



2. Early gr^oivth stages: nuclear plate. In all three species of Noto- 

 necta, there is present during the greater part of the growth period, 

 a characteristic deeply staining mass applied to the nuclear wall. 

 This takes the chromatin stains of haematoxylin and saffranin, 

 but is purple when stained according to Benda's method, and is 

 evidently of mitochondrial nature. In the earliest growth stages, 

 the body is more or less spherical, and may be closely applied to the 

 nuclear wall, or may lie free in the cytoplasm (figs. 43, 44, 63-66). 

 The mitochondrial body flattens down so as to form a plate on 

 the outside of the nuclear membrane ; it is in this form during the 

 spireme stage (figs. 45-53, 67, 74). In N. undulata, at the time 

 when the spireme is disappearing, there is a peculiar bulging of the 

 nuclear membrane at the place where the nuclear plate is attached 

 (fig. 68) . On the nuclear side, chromatic substance is present in 

 the swelling, and in the cytoplasm there is a mass of mitochondria 

 in this region ; this differentiation is clear with the Benda stain 

 (fig. 116). Up to this time, there are practically no mitochondrial 

 bodies present except the nuclear plate. The mitochondrial 

 mass which appears outside the nuclear plate is composed of small 

 spheres and fibers. The bulging very soon disappears, the plate 

 flattens down again with the membrane (fig. 69), and the mito- 

 chondria become distributed through the cytoplasm (fig. 117). 

 The nuclear plate gradually disappears; in N. insulata it becomes 

 conical or spherical in the later stages and apparently may sepa- 

 rate from the nuclear membrane (fig. 55). 



In haematoxylin preparations, the plate when viewed from 

 above appears as a spongy mass (fig. 53 B). When viewed from 

 the side one or two small granules in many cases are seen pro- 

 jecting from the surface; these may be centrosomes. This is 

 suggested further by the peculiar modification of the protoplasm 

 in their vicinity, giving the appearance of an idiozome or attrac- 

 tion-sphere which lies as a cap over the nuclear plate. The origin 

 of these granules cannot be conclusively shown, although in the 

 early stages a small granule may be often detected in the modified 



