42 Papers from the Marine Biological Laboratory at Tortugas. 



After synizesis the oocyte begins a period of very rapid increase in 

 size as well as a very rapid increase and alteration of its chromatic sub- 

 stance. Comparison of the youngest with the full-grown oocyte shows that 

 during the growth-period the nucleus increases in volume about 8,000 times 

 (20 diameters). Oocytes showing the first stages in the disentangling of 

 the spireme from synizesis are abundant. All of them show the nucleolus 

 intact and still highly chromatic (figs, n, 12, 13, 14, 15). Later stages 

 show that the stout primary thread becomes double (figs. 19, 20, 21, 22, 26). 

 \\"\i\\ iron hematoxylin and orange G the moieties stain intensely black 

 throughout. The threads have regular swellings (chromomeres) along their 

 entire extent, giving the appearance of a string of beads. With Auerbach's 

 stain the picture differs somewhat. Only the " beads " stain green, while 

 the remainder of the threads and network stain red. There is evidence 

 here. I believe, in support of the view now very generally held by investi- 

 gators that linin (paranuclein, O. Hertwig) and chromatin are closely re- 

 lated chemical substances and of equally important physiological value. 



The double thread begins to divide transversely into a number (18?) of 

 segments, as occasional specimens clearly show (figs. 20, 22, 23). Some- 

 times the spireme appears to segment while yet single (figs. 16, 17, 18). 

 The pairs of beaded rods scattered through the nuclear reticulum undergo 

 various transformations. They shorten, grow stouter, and often appear to 

 unite at their ends, giving a ring form (fig. 25). Whatever shape they 

 assume ring, rod, sphere, or irregular mass of chromatin (figs. 24, 25, 

 26, 27) they very generally have a mossy or feathery appearance at this 

 stage. This is probably due to a transfer of chromatin from the chro- 

 mosomes to the nucleolus through the nuclear reticulum. The reticulum 

 stains more intensely at this stage with basic dyes and at its culmination 

 the nucleolus has greatly enlarged. Subsequent stages show the chromo- 

 somes reappearing with bilobed forms and sharp contour and reduced size 

 (figs. 28, 29). Ultimately the chromosomes become grouped in a mass 

 (sometimes several masses) where they persist as much-reduced bilobed 

 bodies (figs. 30, 33, 34, 41, 42) until they are taken into the first polar 

 spindle at maturation. 



The later stages in the development of the oocytes above outlined are by 

 no means sharply defined. Transition from one to the other is more or less 

 variable as to characteristic forms and the time of its appearance. This is 

 probably due to the fact that the amount of chromatin in the germinal 

 vesicle of different oocytes of the same age (as reckoned by size of nucleus) 

 varies somewhat. Apparently the process of chromosome formation and 

 chromatin absorption and elimination is hastened in some eggs and retarded 

 in others. 



The extreme minuteness of the cells and the total absence of division 

 figures preclude all observations on synapsis, and consequently deny the sole 



