D. Keilin 
219 
haemalum or haematoxylin, showing neither granules nor vacuoles. The 
micronucleus (Figs. 2 and 3, m.) appears as a small chromatic granule, 2/x to 
3 /jl in diameter, and usually lies in a small peripheral depression of the macro¬ 
nucleus. Its apparent position depends on the orientation of the body of the 
parasite, and varies from a marginal to a central position, but careful examina¬ 
tion shows that its position is superficial on the macronucleus, sunk into a 
shallow depression or notch. In a few cases in which I have observed the 
Fig. 2. Lambornclla stegomyiae, showing the cytostome, Cy .; micronucleus, m .; macronucleus, M. 
V. 
Fig. 3. Lambornclla stegomyiae. A group of six specimens of this ciliate as seen in one field of the 
microscope. Letters as in Fig. 2. 
micronucleus widely separated from the macronucleus, the latter invariably 
showed an empty depression, from which the micronucleus had doubtless been 
displaced accidentally. In addition to the two nuclei, the protoplasm contains 
one to four vacuoles which stain uniformly with basic dyes. Notwithstanding 
its purely parasitic mode of life, Lambornella possesses a small cytostome. The 
cytostome is difficult to see in fixed and stained specimens, and I thought at 
first that I was dealing with a ciliate belonging to the group of the Astoma, 
