with its differentiated cell-body or protoplasm, and its cell kernel or nucleus, has at one time existed. But the various supposed instances of the survival to the present day of such simple living things--described by Haeckel and others--have one by one yielded to improved methods of microscopic examination and proved to be differentiated into nuclear and extra-nuclear substance. [Illustration: FIG. 36. Further stage in the division of the sexual cell drawn in Fig. 35(_e_), showing the _twelve_ chromosomes of the two nuclei of the sperm-cells resulting from the division (_twelve_ instead of _twenty-four_).] The question of ‘spontaneous generation’ cannot be said to have been seriously revived within these twenty-five years. Our greater knowledge of minute forms of life, and the conditions under which they can survive, as well as our improved microscopes and methods of experiment and observation, have made an end of the arguments and instances of supposed abiogenesis. The accounts which have been published of ‘radiobes,’ minute bodies arising in fluids of organic origin when radium salts have been allowed to mix in minute quantities with such fluids, are wanting in precision and detail, but the microscopic particles which appear in the circumstances described seem to be of a nature identical with the minute bodies well known to microscopists and recognised as crystals modified by a colloid medium. They have been described by Rainey, Harting, and Ord, on different occasions, many years ago. They are not devoid of interest, but cannot be considered as having any new bearing on the origin of living matter.