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The early literature on the origin of yolk contains numerous studies which assert that a close morphological relationship exists between the developing yolk masses and certain cellular organelles. The nucleus, mitochondria, Golgi material, and ergastoplasm have all, at one time or other, been implicated in the synthesis of yolk and of other types of secretion as well (@ Bowen, 2; Wilson, 12). The description of the fine structure of the ergastoplasm (endoplasmic reticulum), coupled with the firm evidence for the synthesis of protein involving ribosomes, has led investigators to look for evidence of a close morphological relationship between the genesis of the protein-rich secretion granules and the elements of the endoplasmic reticulum. Studies have been reported where large secretion masses appear within the cisternae of the endoplasmic reticulum (cf. Porter, 8, for literature). However, the best documented studies which seem to involve the endoplasmic reticulum in the synthesis of protein secretion are those of Palade (7) and Siekevitz and Palade (9-11). They present evidence which suggests that in the guinea pig pancreas the ribosomes synthesize the enzymes which traverse the cisternal membranes and gave rise to the relatively large intracisternal granules; the latter probably have chemical properties similar to those of the definitive zymogen granules. How the intracisternal granules are delivered to other regions of the cytoplasm is not clear; they may exit in some way through the cisternae of the Golgi complex. It is interesting to note that similar intracisternal granules are not found in the pancreas of the mouse (5) or rat (7). Large, dense granules of unknown significance have also been reported within the cisternae of the endoplasmic reticulum of the spider oocyte (1). In the course of a preliminary study on the fine structure of the crayfish egg it was noted that the endoplasmic reticulum possessed sharply defined intracisterna] granules. The fact that this condition is infrequently found in other cells seemed to warrant a description of it here.

INTRACISTERNAL GRANULES OF THE ENDOPLASMIC RETICULUM IN THE CRAYFISH OÖCYTE