I proposed an explanation of the origin and significance of the crescent different from all others. I considered the crescents to be syzygies of the parasites of the second group. B}^ syzygies zoologists understand forms which develop from the copulation of several individuals-a kind of sexual hybrid; this is a phenomenon known to occur among different sarcodinia, sporozoa, and flagellates. Moreover, in certain blood gregarines of the frog and the lizard, which are nearly related to malarial parasites, these unions (congregations) have been seen; so, too, in Drepanidium princeps and Karyolysus lacertarum (Labbe).

The fact is that in cases of infection with parasites of the second group blood corpuscles are frequently found containing two or more parasites; and I have several times directly observed the phenomenon of two such approximated parasites blending (melting) together.

For the grounds on which I based my conclusion that the crescents are syzygies of the ameboid parasites I refer the reader to my monograph on malarial parasites. I present here only those points which are explained by no other interpretation of the origin of the crescent. These pertain to the late period at which the crescents appear in the blood, the relatively small number of them in comparison with that of the ameboid parasites, and the obstinacy with which they remain in the blood and resist quinin. All these uncommonly striking circumstances are explained easily by the theory that the half moons are syzygies.

My view was adopted by Manson, who regarded as organisms of copulation not only the crescents, but all parasitic forms that show the power of producing flagella.

Other writers, as Bastianelli and Bignami, Thayer and Hewetson, Ziemann, have failed to find in the blood the morphologic criteria on which I have based my view. One of these, namely, the arrangement of the pigment in figure of eight forms, is so frequent that it is unintelligible to me how it can be overlooked. Other more convincing phenomena, like the proof of copulation in natural and stained preparations, require, to say the least, very painstaking investigations. I see as yet no reason to deviate in the slightest from the standpoint taken by me in my earlier communications. The negative findings of the opposition cannot contradict what I positively and with all certainty observed.

Finally, we must especially insist on the extraordinary vitality of the crescents, in which they differ decidedly from every other form of the different parasites. Days, weeks, and months they may be seen in the blood, though the patient may be taking the largest amounts of quinin.

The relations of the malarial parasites to the red blood corpuscles are evident from the following: The newly formed young parasites (so called spores) remain only a short time in the plasma before they attach themselves to a red blood corpuscle. They remain attached to the surface of the corpuscle but a short time, and then force their way into its substance, where they complete their development. This does not always terminate in multiplication; since, for unknown reasons, sporulation sometimes fails to occur. In these cases, after the parasites have reached a certain size, they break through the remnant of the corpuscle surrounding them and are found free in the plasma, where they often break up into several pieces of different sizes. All these organisms are to be looked on as degenerated parasites in which no further development occurs. Excepting the short period between the throwing off of the spore and its entrance into a corpuscle, all the stages of development take place within the red blood corpuscle.

Under the influence of the parasite, the red blood corpuscles undergo manifold metamorphoses. In the case of the pigment producing parasites, the blood corpuscles are often more or less quickly decolorized, so that their remains are sometimes scarcely visible. Moreover, changes in size and shape of the red blood corpuscles are frequently observed. In tertian fever the infected corpuscles are often hypertrophied even as much as twice to four times the normal size, and at the same time decolorized. On the other hand, diminution in size of the infected corpuscle is also observed, as in the case of the

"globuli rossi ottonati," first described by Marchiafava and Celli. It is these shrunken red blood corpuscles that show the color of old brass. They occur in cases of infection with the faintly pigmented parasites of the second group. For the sake of brevity, we describe them as "brassy corpuscles" (Messingkorperchen). The markedly pigmented small parasite lies sometimes in what appears like a rumpled white veil, consisting of the shrunken, completely decolorized corpuscle.

The corpuscles infected by the quartan parasites are often somewhat diminished in size, more deeply colored, but without other signs of shrinking.

It is not our purpose to go into details concerning the structure of the parasites, yet we may say that they show plasma, a nucleus, and a nucleolus. (See Plates VI and VII.)

Danilewsky observed, in two cases of chronic malaria , bodies within leukocytes, which he designated as pseudocysts and leuko cytozoa. Nothing at present can be said in regard to their relation to the malarial parasites or to malaria in general.