Let us glance at Driesch's illustration from the phenomena of 
Group (a.); the example which he has developed as a proof of 
Neo- Vitalism — the development of the sea-urchin's egg. The usual 
cleavage of the fertilised egg cell results here in first two and then 
four equal cells. Further segmentation gives, by equal division 
again, an eight cell stage. Driescli was able to show by separating the 
blastomeres (by shaking) that even in the eight cell stage, each blas- 
tomere was capable of producing a complete sea-urchin larva. After 
separation of the blastomeres in the following sixteen-cell stage 
(separation by the use of sea-water free from calcium), some of the 
isolated cells might yet survive and give rise to perfect larvae. The 
blastomeres in this ease are, therefore, totipotent, or at least so up to 
the sixteen-cell stage. If we assume that a mechanism is present in 
the developing egg, the mechanism must be capable of division with- 
out destruction of the character of the whole, and must be present in 
each blastomere of the eight-cell stage at least. Let us follow the 
argument of Driescli still further. If cleavage is allowed to continue 
until the blastula stage is reached, this must possess a 
three-dimensional mechanism if we assume that a “kind of real 
machine" exists in the system “which if once set going, would result 
in the differentiations that are to take place." For a machine whose 
acting is to be typical with regard to the three dimensions of space 
must be typically constructed in regard to these dimensions itself. 
We can, however, cut the blastula in pieces and the parts will give 
rise to complete embryos. Can you conceive of a machine which 
can remain itself, if you remove parts of it or if you rearrange the 
parts at will? And Driescli has come to the conclusion that if we 
are to explain the development of the sea-urchin egg (which is a 
harmonious-equi potential system) by the action of physical or chem- 
ical factors, there must be some such thing as a machine. 
Driesch's experiment, however, proves perhaps no more than 
that no mechanism such as is understood above can be present in 
the developing egg and embryo. The fact alone that part of a 
sea-urchin blastula can give rise to a complete larva does not seem 
to my mind to indicate very much more than the fact that the germ 
cell can give rise to a larva, for in both cases it is almost impossible 
to conceive of a series of chemical changes due to a certain initial 
chemical constitution being alone responsible for the regulation 
of development. And if it were found possible to explain the devel- 
opment from the egg as due to a chemical mechanism alone, it would 
be just as probable that the development of isolated blastomeres of 
the sea-urchin's egg could be explained by the same process. 
Bearing in mind, then, the possibility of some other chemical 
mechanism, let us follow the development of the egg of another 
organism, for it will be found that the sequence of events described 
above is not universal and we should hope that our theory of devel- 
opment would apply to all cases. The development of the egg of 
