1897.] Natural Impulses. 583 
The author by these remarks does not intend to dispute the 
possibility and even probability, that new species have sprung 
from former ones in the course of unmeasurable past times ; 
on the contrary, there are numerous geological, botanical and 
zoological facts known, which irresistibly point in that direc- 
tion, but in historic time, i. e., during the last 5000 years, no 
evident change is known to have happened. Plants, animals 
and people represented on old Egyptian and Assyrian sculp- 
tures are exactly the same as those existing nowadays. The 
time, when linking forms between lizards and birds, as the 
pterodactylus, were living, lies in a remote past, and the origin 
of existing transient forms, as ornithorhynchus, lepidosiren 
and amphioxus may without scruples be dated back to periods 
preceding the appearance of man. Perfectly agreeing to the 
view adopted by most naturalists of our time, that plants as 
well as animals are the results of gradual evolution originating 
from monocellular organisms, we find it supported by the con- 
vincing argument of the descent of every single being from a 
minute fertilized cell, the embryo of man itself in its first 
stages closely resembling those of other animals, differences in 
the accomplishment of organs appearing in the advanced 
periods of growth. 
By the comparison of any forms of higher animals including 
insects, evidence is given of a principle or type of symmetric 
structure common to all of them. There is a head provided 
with partly bilateral organs for the reception of objects and 
impressions from the outside and ending in a chord of nervous 
substance, the spine, located on the back or front side of the 
body, and dividing it into two longitudinal halves, to which 
the organs of movement are attached equally distributed on 
both sides, one side being the reverse of the other one. Simi- 
lar pervading principles of structure are found in lower ani- 
mals, more or less varying according to the classes and families 
_ to which the beings belong. The structural principles per- 
vading the vegetable world are different, but not less evident 
and striking ones. One of the chief features in higher plants 
is the constant repetition of the same number, or a multiple of 
it in the parts of the flower and the fruit. . In many families 
