"III. Formation of stock companies . Thereby: 1) An enormous expansion of the scale of production and of enterprises, that was impossible for individual capitals. At the same time, enterprises that were formerly government enterprises, become public.
2) The capital, which in itself rests on a social mode of production and presupposes a social concentration of means of production and labour-power, is here directly endowed with the from of social capital (capital of directly associated individuals) as distinct from private capital, and its undertakings assume the form of social undertakings as distinct from private undertakings. It is the abolition of capital as private property within the framework of capitalist production itself.
3) Transformation of actually functioning capitalist into a mere manager, administrator of other people's capital, and of the owner of capital into a mere owner, a mere money-capitalist. ...this total profit is henceforth received only in the form of interest, i.e.., as mere compensation for owning capital that is now entirely divorced from the function in the actual process of reproduction...
... this is the abolition of the capitalist mode of production within the capitalist mode of production itself, and hence a self-dissolving contradiction, which prima facie represents a mere phase of transition to a new form of production. ... It is private production without the control of private property."
marx, _capital, v3_, pp.427-29.
now, clearly marx regards this as important from the perspective of a transitional phase, of preparing the ground for the abolition of capitalism as such. I am not so sure of this. however, marx does see this as something which falls outside the definition of capitalism as the reign of private property. that he regards this as a "self-dissolving contradiction" would be to continue to define capitalism as the reign of private property, such that it is treated as 'anomalous'. it is certainly contradictory, and it certainly embodies the antagonisms of capital in a different way to that of personalized and direct ownership, but there is an objectivist catastrophism inherent in the above passage (taken on its own) which continues to think of the joint stock company as an anomaly when it, like the rescheduling of credit, has become a condition of stabilization (or at least a new regime of capital's momentary stability).
engels in _anti-duhring_ goes further:
"... the transformation, either into joint-stock, or into state ownership, does not do away with the capitalistic nature of the reproductive forces. In the joint-stock companies this is obvious. And the modern state, again, is only the organisation that capitalist society takes on in order to support the capitalist mode of production against the encroachments as well of the workers as of individual capitalists."