1915] IIUTCHIXSOX— ABIES BALSAMEA 461 



pervaded by fibers radiating from irregular centers (fig. 51). In 

 the egg of Abies there is an excessive development of intranuclear 

 fibers. It seems reasonable to suppose that they originate from 

 cytoplasmic material which has entered the nucleus during its 

 growth period, and which may be differentiated into the fibrous 

 form under physiological conditions not yet determined. 



The slender filaments pervaded by small granules are scattered 

 throughout the greater part of the nucleus. They are mqst 

 definitely organized at the time when the spindle fibers are most 

 conspicuous (figs 27, 3$, 42). When the fibers disappear, the fila- 

 ments become disorganized, resulting in a granular mass (figs. 43, 

 46); when the spindle fibers appear the second time, the whole 

 nucleus becomes more or less fibrous (fig. 51); when the daughter 

 nuclei are formed, these bodies are not included, but form a matrix 

 for the nuclei (figs. 49, 50). We may conclude that these filaments 

 also are cytoplasmic, resembling the spindle fibers in nature, and 

 becoming differentiated under similar conditions. 



Pairing of chromosomes in fertilization 



The succession of events which occur in connection with fertili- 

 zation and the first division of the zygote has been traced not only 

 by a consideration of the stages in the approximation and redistri- 

 bution of chromatin bodies, but also by tracing parallel series of 

 changes in the size of the nucleus, in the modifications of the deeply 

 staining food bodies, and in the formation and dissolution of spindle 

 fibers. A study of the chromatin, involving as it does the union 

 of the male and female elements and distribution in the daughter 

 nuclei, is of primary importance. Emphasis has been given first 

 to a study of the related phenomena, already described, thereby 

 eliminating, in so far as is possible, the possibility of a misinter- 

 pretation of the order of events. 



The approximation of male and female nuclei has been described 

 for a number of conifers. In general the process as found in Abies 

 agrees with that of these descriptions. A few features may be 

 noted. No cytoplasm could be detected adhering to the male 

 nucleus as it approached the egg nucleus. There is a great disparity 

 in the sizes of the pairing nuclei; that of the egg, as shown in fig. 19, 



