This paper deals with observations made on sections of cross-fertilized eggs of two kinds: (1) Toxopneustes eggs fertilized with Moira sperm, (2) Arbacia eggs fertilized with Moira sperm. The results of the study may be summarized as follows: 1. The equatorial plate of the Moira-Toxopneustes cross shows a mixture of two kinds of chromosomes not sufficiently unlike one another to enable a positive distinction between the two. 2. The equatorial plate of the Moira-Arbacia cross shows a mixture of two kinds of chromosomes, one variety long, the other variety short. These differences in form are correlated with the spermatozoön and the egg respectively.