Protoplasmic Connections of Adjoining Cells 39 
in equilibrium in both the corresponding phylogenetic 
forms. To effect the transition it is necessary then that 
in each ontogenetic stage there suddenly supervene at 
some point of the system a change, which disturbs the 
established equilibrium and provokes the passage of the 
continuous nervous flux to a new dynamic equilibrium. 
If the intercellular bridges have really the significance 
which we have attributed to them, one can see how they 
must be present in all organisms and in all stages of 
development. It is superfluous to go more thoroughly 
here into the fact that this is exactly what is fully 
confirmed by histologic investigations which are being 
ever more carefully prosecuted. 
We recall for example the protoplasmic connection 
observed by Hammar between the segmentation spheres 
of the sea urchin egg: The cells of the blastula are 
covered all over the outside of it by a protoplasmic layer 
which adheres in each cell only to the part of its surface 
which is directed toward the outside. This layer in a 
few preparations not sufficiently protected against drying 
separated itself a little from the blastula. There appeared 
then thin filaments, variable in number and more or less 
regular in disposition, which extended from the granular 
protoplasm of the different blastomeres to the interior of 
this layer and produced in this way a manifold connection 
of the different cells with one another.’® 
Sedgewick has observed the same thing in the develop- 
ment of the eggs of Peripatus. The two cells which 
come from the cleavage of the eggs are not completely 
15Hammar: Ubereinen primaren Zusammenhang zwischen den 
Furchungszellen des Seeigeleies. Archiv fiir mikrosk. Anat. und 
Entwicklungsgesch. Bd. XLVII. Erstes Heft. Bonn, Cohen. 1896, 
P. 14ff. 
