The effect of experimentally induced changes in consistency on protoplasmic movement

Abstract

Agitation by means of a micro-dissection needle tends to cause the protoplasm of a living cell to pass from a more solid to a less solid phase.

In marine ova, where one can closely follow the solidifying of the protoplasm just prior to cell division, mechanical agitation will cause the protoplasm to revert to its original liquid state so that the egg reverts to the shape of a sphere. If the egg so treated be subsequently left undisturbed the solidifying process starts up again with the result that the egg undergoes normal cleavage.

In a previous communication 1 the writer has described the structural relations of changes in protoplasmic consistency of the Amæba to the formation of pseudopodia. The maintenance of pseudopodia depends upon a relatively solid state of certain parts of the Amæba.

A resting Amæba, with numerous slender pseudopodia all over its surface, is relatively solid. Upon mechanical agitation the pseudopodia are retracted as the Amæba becomes more liquid. Fresh pseudopodia in an agitated Amæba tend to be broad lobate and, if the agitation be continued, all of the Amæba liquefies. The entire body then becomes, as it were, a single pseudopodium with a peripheral current of granules flowing away from its anterior end and a central current flowing forward. An Amæba in this extreme state does not change in position as the back flow tends to equal the forward flow. Amæba which are experimentally brought into this state have, so far, not been observed to return to their previous condition. The rate of flow of the currents gradually slows down until the animal dies.

The protoplasm of an Amæba exists in a certain normal state of consistency from which it may deviate so as to solidify on the one hand or liquefy on the other.