Toxoplasma gondii undergoes schizogony and microgametogony in the epithelial cells of the cat ileum. On the basis of cytoplasmic structures, it is impossible to distinguish between the early stages of these processes but nuclear differentiation appears to have occurred. In the early schizont the chromatin is distributed in small patches throughout the nucleus but in the nucleus of the microgametocyte the chromatin is condensed into a few large areas. In the schizont, the first distinguishing cytoplasmic features are the appearance of the dome‐shaped membranes of the merozoite anlagen. In the schizogonic process, nuclear division precedes merozoite formation which occurs by multiple internal budding in a manner similar to endodyogeny. The appearance of flagella is the first cytoplasmic feature to distinguish the microgametocyte. Microgamete formation is similar to that reported for other coccidian species. The microgamete consists of a dense elongate nucleus anterior to which is a single mitochondrion. The anterior consists of a perforatorium and two flagella between which 4 microtubules run longitudinally.

Of course, mass radiography has widened its scope since its introduction in the early 1940s. It has become a service, a tool for presymptomatic diagnosis. X-ray departments in hospitals are neither meant nor equipped to do this. To destroy such a service without even taking regional differences and problems into consideration is a retrograde step.-I am, etc.,

No abstract

No abstract

SynopsisA Histological investigation has been made of growth and repair of periostracum in Mytilus edulis. Physical rather than chemical differences in the processes of secretion can account for the variations in the structure of periostracum which appear during normal growth and in that which follows damage. Amœbocytes take part in the production of periostracum by supplying material for the secretory cells. Reasons for the presence of other granular cells near the site of secretion are also suggested. The periostracum is secreted solely by the epithelium of the inner surface of the outer mantle fold, although initially it adheres to the epithelium of a process of the middle fold. Consideration of the nature of the connection of the periostracum with its retractor muscles leads to the hypothesis that the cells of both epithelia move with the periostracum towards the mantle edge. The tissue where the two epithelia meet appears to be meristematic.