The stars are taken from a working list of 150 stars, which may eventually be extended to include all stars down to the fourth magnitude, and it is expected that in the course of time the motions of about 300 stars may be spectroscopically determined.

Neither can we discover whether organisms here are capable of attaining the average development of organisms in other of the planets that are probably circling round most of the myriads of stars, whose physical constitution, where-ever it has as yet been observed spectroscopically, does not differ much from that of our sun.