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. 15 



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 



lc Hammar: Ubereinen primaren Zusammenhang zwischen den 

 Furchungszellen des Seeigeleies. Archiv fur mikrosk. Anat. und 

 Entwicklungsgesch. Bd. XLVII. Erstes Heft. Bonn, Cohen. 1896. 

 P. I4ff. 



