304 NATURAL SCIENCE. APRIL, 
In regard to the scientific utility of these researches in experi- 
mental embryology, it may be noted that a number of general results 
are very clear. (1.) There is a great deal of life in an egg. Three- 
quarters, a half, a quarter will in favourable conditions form a com- 
plete larva. (2.) There is no little plasticity in the germ; the 
segmentation may be profoundly altered, the shape of the young 
embryo may be greatly changed, and a new type of larva may be 
produced. Yet the inherited characteristics are strong, for the ex- 
periments show a marked tendency in the germ to reach a normal 
result even by an abnormal path. (3.) To analyse out a definite 
factor—say osmotic pressure—in teratogeny is beyond dispute 
useful, for it may help us not only to understand malformations 
occurring among higher vertebrates, but also to get nearer an under- 
standing of the conditions of normal development. (4.) As every- 
one knows, there are few facts, or, some would say, no facts, which 
can at present be cited with confidence as direct evidence of the 
transmission of environmentally-produced variations; and Weis- 
mann’s case against the possibility of acquired somatic variations 
specifically affecting the reproductive cells is strong enough to lead 
many to depreciate, except in the case of simple Protozoa and 
Protophyta, the direct influence of the environment as a factor in the 
origin of transmissible variations. Be that as it may. How many 
ova are there which float in the sea and in other media; these are 
now, as similar ova have been in the past, exposed to the influence of 
very complex physical and chemical conditions; that their living 
stuff may be greatly affected the results of experimental embryology 
show ; it is likely that the same is true in Nature’s great laboratory ; 
and the results, being germinal, may be transmissible. We need not 
be in haste to exclude the direct influence of the environment from 
among the primary factors of evolution. 
One practical application occurs to me. Many abnormalities in 
the segmentation of the ova of littoral animals, ¢.g., Gasteropods, 
have been noticed by various zoologists. The other day, in examining 
the ribbons of eggs which Doris lays in such abundance on the 
low-tide rocks, I noticed the great frequency of twins and triplets. 
In some cases they seemed to preponderate. Is it not likely that an 
explanation may be found in the fact that the ribbons are battered to 
and fro by the surge? Whatisdone in the laboratory may also occur 
on the shore. The shaking may separate the segmentation-cells and 
mechanically produce twins. This is, of course, nothing more than a 
suggestion, in default of the obviously necessary experimental 
verification, but I find an interesting confirmation in C. Chun’s 
observation that twin Ctenophora were most abundant after stormy 
days. 
