ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
611 
comment is made that while the morphological side of their phytogeny 
can be constructed with some success, their physiological origin is quite 
unknown. In endeavouring to throw light upon the origin of sexual 
dimorphism and on the wider problem of the origin of species, the 
author emphasizes the importance of the blood, as bringing into connec- 
tion the organs of the body, and thus enabling one organ to influence 
another which is at a distance from it. Of the importance of the con- 
stituents of the blood many illustrations can be given ; the evil effects 
often following transfusion of blood, many facts of bacteriological inves- 
tigation, the influence of the extirpation of the thyroid or of the supra- 
renal bodies, and so on. The last of these examples especially shows 
what an important effect the products of the metabolism of one organ 
may have on the whole organism. The author therefore concludes that 
secondary sexual characters are directly due to the varying reactions 
of the organs of the body to the chemical stimuli which pass out from 
the sexual organs. 
With regard to the theory of the germ-plasm, the importance of 
self-induced variations of its elements is especially dwelt on. If the 
germ-plasm, as the undying substratum in perishable organisms, begins 
to vary, it is conceivable that during successive generations it will 
continue to vary in the same direction unless new influences alter this 
direction. Free crossing would of course prevent this, but if the neces- 
sary conditions of isolation are preserved we might have a new form 
produced without either natural selection or the influence of environment 
having had any direct effect. These considerations lead the author to 
the conclusion that there are three types of variation: (1) The primary 
variations “ wdiich are the result of intimate changes in the germ-plasm, 
and which result in the formation of new kinds of ids, or in the alteration 
of the existing kinds. These variations are inherited, are apparently 
from their nature progressive, and may lead to the formation of new 
species.” (2) Secondary variations ; these arise from different combina- 
tions of ids which are already present in the germ-plasm, and are 
produced by the conjugation of cells. They are inherited and lead to 
individual variation ; they may however be fixed by isolation and so 
lead to the formation of species. (3) Tertiary variations, the result of 
the action of environment on the organism, are not usually inherited. 
With regard to the inheritance of acquired characters, variations of 
the third type, the author has a new hypothesis to put forward. He 
believes in the inheritance of certain acquired characters, such as the 
epilepsy of the Brown-Sequard experiments. He considers that in 
such cases the modified activity of certain of the organs results in the 
formation of certain products, probably ferments, which are taken up 
by the reproductive cells, and, without forming an integral part of the 
germ-plasm, are handed on to the developing organism, and during 
the development and future life exercise their proper influence upon 
function. This accessory part of the germ-cell he calls the zymoplasm. 
The paper concludes with a careful consideration of the part played 
by Natural Selection, in which the author emphasizes the definiteness 
of variation, and the fact that natural selection tends to eliminate the 
bad rather than to preserve the good, so that its action must be 
negative rather than positive as is artificial selection. On this point 
1893. 2 U 
