The fine structure of the body-wall in Ascaris lumbricoides was investigated by electron-microscopical techniques. The body-wall is composed of a cuticle, epidermis, and a single layer of muscle cells. The cuticle contains several layers: a superficial membrane, a cortex, the ‘fibrillar layer’, a matrix or homogeneous layer, 3 fibre layers, and a basal lamella. The cortex is divided into a homogeneous, external cortical layer, and a fibrous, internal cortical layer. The ‘fibrillar layer’ is a series of canals which extend from the inner part of the matrix layer to the cortex. The canals have distinct walls but no contents were demonstrated. No fibres or lamellae could, be detected in the matrix layer. The strands of the fibre layers and the basal lamella are formed from fine fibrils, less than 10 m in diameter. There is an inner system of canals that links the epidermis with the basal lamella and the fibre layers. The epidermis has a network of fibres, some of which attach the muscle cells to the cuticle. The muscle cell contains myofilaments of 2 types, an array of large filaments about 30 m. in diameter, each surrounded by a number of smaller filaments about 5 to 7 m in diameter. Glycogen occurs in the epidermis and muscle and is identified as granules; there tends to be a clumping together of granules to form deposits about 100 m in diameter. External to the sarcolemma lies a connective tissue sheath which contains collagen, probably in the form of fibrillar and particulate material.
The cuticles of young adult Ascaris have a basic structure similar to that of the fully grown worms. During the growth of the adult worm the cuticle increases in volume, and this increase involves all the layers of the cuticle. The homogeneous or matrix layer increases in thickness more rapidly than the fibre layers, and both of these layers grow faster than the cortex. Ribonucleic acid is more abundant in the epidermis of young adults than in the fully grown worms and this is correlated with the development of endoplasmic reticulum and ribosomes. It is suggested that the extensive canal system in the cuticle transports materials to all layers of the cuticle.

The fine structure of the body-wall in Ascaris lumbricoides was investigated by electron-microscopical techniques. The body-wall is composed of a cuticle, epidermis, and a single layer of muscle cells. The cuticle contains several layers: a superficial membrane, a cortex, the ‘fibrillar layer’, a matrix or homogeneous layer, 3 fibre layers, and a basal lamella. The cortex is divided into a homogeneous, external cortical layer, and a fibrous, internal cortical layer. The ‘fibrillar layer’ is a series of canals which extend from the inner part of the matrix layer to the cortex. The canals have distinct walls but no contents were demonstrated. No fibres or lamellae could, be detected in the matrix layer. The strands of the fibre layers and the basal lamella are formed from fine fibrils, less than 10 m� in diameter. There is an inner system of canals that links the epidermis with the basal lamella and the fibre layers. The epidermis has a network of fibres, some of which attach the muscle cells to the cuticle. The muscle cell contains myofilaments of 2 types, an array of large filaments about 30 m�. in diameter, each surrounded by a number of smaller filaments about 5 to 7 m� in diameter. Glycogen occurs in the epidermis and muscle and is identified as granules; there tends to be a clumping together of granules to form deposits about 100 m� in diameter. External to the sarcolemma lies a connective tissue sheath which contains collagen, probably in the form of fibrillar and particulate material.

The cuticles of young adult Ascaris have a basic structure similar to that of the fully grown worms. During the growth of the adult worm the cuticle increases in volume, and this increase involves all the layers of the cuticle. The homogeneous or matrix layer increases in thickness more rapidly than the fibre layers, and both of these layers grow faster than the cortex. Ribonucleic acid is more abundant in the epidermis of young adults than in the fully grown worms and this is correlated with the development of endoplasmic reticulum and ribosomes. It is suggested that the extensive canal system in the cuticle transports materials to all layers of the cuticle.