. The eggs of mammals . The events occurring at fertilization in the fallopian tubes have been subject to detailed examination chiefly in poly- ovular mammals, , the rabbit, rat, mouse, ferret, etc. In all cases the sperm surround the ova embedded in the mass of follicle cells, and penetrate to the ova causing the follicle cells to fall away at the same time. That the sperm swarm present in the tubes is actively responsible for the fall- ing away of the follicle cell mass is abundantly evident from numerous recent observations of fertilization in the rabbit (Pincus, 1930; Yamane, 1930, 193
. The eggs of mammals . The events occurring at fertilization in the fallopian tubes have been subject to detailed examination chiefly in poly- ovular mammals, , the rabbit, rat, mouse, ferret, etc. In all cases the sperm surround the ova embedded in the mass of follicle cells, and penetrate to the ova causing the follicle cells to fall away at the same time. That the sperm swarm present in the tubes is actively responsible for the fall- ing away of the follicle cell mass is abundantly evident from numerous recent observations of fertilization in the rabbit (Pincus, 1930; Yamane, 1930, 1935; Pincus and Enzmann, 1932, 1935). As described previously rabbit ova in does mated to sterile bucks begin to separate out of the follicle cell mass by 16 hours after copulation at the earliest, and the process is normally completed between the 17th and 19th hours. In fertile matings free ova have been observed as early as 113/^ hours after coitus, and all ova are invariably free by the 14th hour. Furthermore, when freshly o\ailated ova from sterile matings are placed in vitro with sperm suspensions there is a rapid dispersion of the surrounding follicle cells which does not occur in control cultures of ova in sperm-free media. Similar phenomena have been observed by Gilchrist and Pincus (1932) in the rat (Figures 23 to 25) and by Pincus (unpublished observations) in the mouse. 75 Fig. 23, Rat ovum recov- ered from the tubes at 16 hours after a sterile mating. Note surrounding folUcle cells. (From the Anatomical Record.)
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