Formation of the Egg Shell in Fasciola hepatica as Demonstrated by Histological Methods

Abstract

There appears to be no well-settled conclusion concerning mode of formation of egg shell in Fasciola hepatica. Schubmann (1905) accepted views of many previous and contemporary authors as to role of Mehlis' gland (cochlear or shell gland) in process. Henneguy (1906) concluded instead that yellowish refractile granules, which vitelline cells contain and liberate in abundance, play principal part in supplying shell-forming substance. Leuckart, according to Henneguy, accepted this view. Henneguy also noted striking resemblance of Mehlis' and prostate glands, and suggested secretions of two were similar in character and function. Goldschmidt (1909) thought yellow granules first described by Henneguy, represented only substance involved in shell formation and supported Henneguy's interpretation of Mehlis' gland function. Tyzzer (1918) assigned to secretion of Mehlis' gland an important accessory role in process. He found in Collyriclum faba, a trematode of sparrows, that globules are liberated suddenly and almost completely from vitelline cells when they reach o6type, and pointed out that conditions which induced these changes are localized in region where secretion of Mehlis' gland is discharged. He comments: The presence of peculiar granules in cytoplasm of these shell gland cells, and in their slender protoplasmic processes extending to o6type, is strongly indicative of a secretion of specialized type rather than an inert one in which ova float as proposed by Goldschmidt. Augustine (1929) refers to Tyzzer's work, and states that in trematodes the shell (egg) is probably derived from fusing together of liberated yolk granules, while glands (Mehlis' gland) surrounding o6type probably secrete a liquid in which ova are suspended. He does not, however, seem to concur in Tyzzer's contention that secretion of Mehlis' gland must contribute something essential to process of shell formation. Brumpt (1936) in a foot-note referring to Henneguy's work (1906) remarks that trematodes like Sanguinicola and Zoigonus, which lay eggs normally, do not have cochlear (Mehlis' gland) cells. One of us (Kouri), first stimulated by pathological material derived