Abstract
In agreement with earlier descriptions (Thornberry, Eisenstark & Anderson, 1948; Hickman, 1955), electron micrographs revealed that the phage has a polyhedral head, which, via a neck region, connects with a contractile tail. The phage head has a hexagonal outline, 600 Å across opposite apices.
The neck connecting the phage head and tail is 80 Å in length, but the exact point at which it connects to head and tail is not clearly defined. The contractile tail is composed of an outer sheath and a central core, terminating with a base plate. Attached to the base plate are six tail spikes, each 100 Å long. In its extended form the sheath is 800 x 200 Å, with 20 cross bands (Pl. 1, fig. 1, 2).