[Ultrastructure of the endoplasm of ophryoscolescides].

The digestive system of the Ophryoscolescides includes different parts : the adoral ciliary zone, the cytostome, the oesophagus, the endoplasm, the rectum and the anus. The endoplasm appears as a digestive sack surrounded by the mesoplasm. This fibrillary envelop separates it from the ectoplasm. It's in the endoplasm that the mechanism of the digestion develops. The endoplasm contains many different structures. It includes macrovesicles of three types, bacteria, plant-particles, microvesicles of two types, ergastoplasm, polysaccharides, the Golgi apparatus and fibrils. The macrovesicles of the first and the second type are not to be found simultaneously in the same endoplasm. The macrovesicles of the third type, very few in number, are different of the previous ones by their double membrane and their denser granulations. Large-sized vesicles contain bacteria at different stadia of digestion. At the end of the digestion, the bacteria are completely or partially degraded. The plant-particles ingested by the Ciliate are to be found in the endoplasm, surrounded by a vesicle. A first type of microvesicles are found in the oesophagus and in the rectum. They are distinguished by a deep black coloration of variable shape. Another type of microvesicles is also present in the endoplasm. They are small bright vesicles that can bud from large-sized vesicles. In the endoplasm the ergastoplasmic lamellae and rings are easily recognizable thanks to the ribosomes, that edge their external membrane. The ribosomes are also situated along the mesoplasm, around polysaccharidic grains and in small groups between the other endoplasmic elements. The polysaccharidic grains are netting-needle shaped bodies. Noirot-Timothee confers them a reserve function. The Golgi apparatus includes eight to eleven saccules. The extremities of those saccules present swellings or golgian ampullae. The endoplasm is also strewn with fibrillary structures that, cross-section are arranged in groups of four or five tubules. This type of endoplasm is found in Ophryoscolescides taken from a ruminant that has been fasting for several hours. In some individuals the endoplasm can have a totally different aspect. It is filled with vesicles of quite different sizes and shapes. The localization test of the acid phosphatase reveals, in this type of endoplasm, lead deposits. These vesicles are probably autophagic vesicles.