. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. THE VITAL PROPERTIES OF THE CELL 263 Thus in the egg of the round worm of the horse the union of the two sexual nuclei, which is the final stage of fertilisation, onlj occurs during the formation of the first division spindle, in vphich process they take an important part. The important principle enunciated by van Beneden is as follows : Half of the nuclear segments of the first division are derived from the egg- nucleus, and half from the sperm-nucleus, hence they may be distinguish
. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. THE VITAL PROPERTIES OF THE CELL 263 Thus in the egg of the round worm of the horse the union of the two sexual nuclei, which is the final stage of fertilisation, onlj occurs during the formation of the first division spindle, in vphich process they take an important part. The important principle enunciated by van Beneden is as follows : Half of the nuclear segments of the first division are derived from the egg- nucleus, and half from the sperm-nucleus, hence they may be distinguished as male and female. Now since in this case, as before in nuclear division, the four segments split longitudinally, and then separate, and move towards the two centrosomes, two groups of four daughter-loops are formed, of which two are of male and two of female origin. Each group then transforms itself into the resting nucleus of the daughter-cell. Thus it is indisputably proved, that each daughter-nucleus in each half of the egg produced by the first division process contains two equal quantities of nuclein, one of which is derived from the egg-nucleus, and the other from the sperm-nucleus. 2. The Fertilisation of Phanero- gamia. The discoveries which have been made concei^ning the processes of fertilisa- tion in Phanerogamia correspond most completely with those which have been ob- served in the animal kingdom. Stras- burger (VII. 38) and Guignard (VII. 15) stand in the first rank of investigators. The most suitable objects for examination are the Liliaceae, especially ii'/utjn martagon and Fritillaria imperialis. One of the cells, into which the pollen grain divides in Phanerogams, corresponds to the sperma- tozoon, whilst the vegetable egg-cell, which in the ovule is enclosed in the ovary of the gynoecium, forms the most important por- tion of the embryo-sac, and corresponds to the animal egg. When the pollen grain has reached the stigma of the style, its contents commenc
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