Given then the fact that variations do constantly and inevitably occur in offspring owing to new qualities arising in germ-plasm itself, it is obvious that these variations are either what are termed "spontaneous," or else they must be due to the action of the surroundings on the germ-plasm. By the term "spontaneous," in this connection, it is not meant that these variations arise without cause or in a haphazard manner. It is simply meant to imply that the present state of our knowledge does not justify us in stating what does actually cause the variation in germ-plasm, or the laws in accordance with which such variations occur. That they must be a matter of cause and effect and law every biologist believes, but until the law can be demonstrated, the term "spontaneous" may well be retained to distinguish these variations from those which arise by the obvious action of environment. For example, the variations which occur as the results of reproduction from two parents, do so because of the mingling of the respective germ-cells, and such variations come under the group of "spontaneous"; whereas changes induced on account of the food supplied, or poisonous substances in fluids surrounding germ-cells are not spontaneous, but environmental. A point of great interest to the embryologists is the question whether the differences of detail which exist between children and their parents are of the nature of spontaneous variations, taking their origin in the germ-plasm itself, or mere modifications produced by the action of the environment of the embryo. Further, should both these factors play a part in producing these differences, which is of greater importance, and in what proportion? This question is elaborated in great detail by Dr. Archdall Reid, in his work, _The Laws of Heredity_, which ought to be read by every intelligent citizen and parent who is interested in the welfare of the young. In the main in this subject we follow the ideas so ably put forward by him. He points out that the offspring of the same parents always differ not only from the parents, but among themselves, even if they be twins, and amongst the lower animals every member of a litter of dogs, or pigs, or kittens, shows differences in size, colour, activities, temperament, and characteristics. Are those differences due to the action of environment on the embryo or do they take their origin in the germ-cells from which the individuals came? Inasmuch as a litter of puppies is subjected to precisely the same environment during the whole time of development, it is perfectly obvious that such differences as they exhibit at the time of birth must have been germinal, an identical environment could not by any stretch of the imagination be held responsible for producing variations. They, therefore, must be of the spontaneous variety. Of course it may be argued that even during development the environment of each embryo within the mother is not