9. It has been said that a criminal conspiracy is a partnership in crime, and that there is in each conspiracy a joint or mutual agency for the prosecution of a common plan. Thus, if two or more persons enter into a conspiracy, any act done by any of them pursuant to the agreement is, in contemplation of law, the act of each of them and they are jointly responsible therefor. This means that everything said, written or done by any of the conspirators in execution or furtherance of the common purpose is deemed to have been said, done or written by each of them. And this joint responsibility extends not only to what is done by any of the conspirators pursuant to the original agreement but also to collateral acts incidental to and growing out of the original purpose. A conspirator is not responsible, however, for acts done by a co-conspirator after termination of the conspiracy. The joinder of a conspiracy by a new member does not create a new conspiracy nor does it change the status of the other conspirators, and the mere fact that conspirators individually or in groups perform different tasks to a common end does not split up a conspiracy into several different conspiracies.