During the months of May and June last three batches of monkeys (Cercopithecus), making fourteen in all, were sent to me for experimental purposes. The first lot of four monkeys arrived on May 15th, and on taking their temperatures the following evening it was found that they all had fever varying from 103·8° to 106·4° F. Blood films were taken and examined the following day, but nothing was then found save a rather marked degree of polychromatophilia. That evening, May 17th, the temperature of one of the monkeys was found to be 110·4°, the animal was moribund, and died within two hours. An autopsy was made next morning, but nothing abnormal could be found. That afternoon, in examining a fresh blood preparation, a non-pigmented pear-shaped endocorpuscular body was found. This body was single, pear-shaped when first seen, and gradually changed its shape, becoming first oval and then again pear-shaped but with the thin end now at the opposite extremity. No protrusion of pseudopodia was observed.