H^EMOPKOTEUS 61 



parasites of the red corpuscles have a developmental relationship with 

 free-moving forms of the true Trypanosome type. 



The best subject for a first examination is Hcemoproteus noctuce, 

 nearly always present in the common owl. It is found with almost 

 equal frequency in other species of owl, as well as in the kestrel and 

 goshawk, and is present in singing birds (finches, larks, thrushes, 

 crows, shrikes, &c.), though infection is here less to be relied upon. 



Typical free-moving Trypanosome forms are difficult to find, but 

 the cell-parasitic, non-flagellate stages are very common. Of these, 

 the following modifications have been described : 



(1) Asexual forms, which are capable of a certain amount of 

 amoeboid movement, and may, consequently, be more or less irregular 

 in outline. They are sickel-, dumb-bell-, or bean-shaped, and throw 

 out conspicuous knob-like projections at the poles. These are some- 

 times frayed out and the organisms may then be mistaken for fission 

 forms. That the knob-like processes do not represent the first stage 

 of commencing new organisms, but are merely protoplasmic processes 

 endowed with amoeboid movement, is proved by the absence of 

 anything in the nature of nuclear division. 



(2) Sex forms (gametocytes), which are incapable of amoeboid move- 

 ment and in which the outline is more regularly bean-shaped, with 

 equally rounded poles. Among these, two forms are distinguished :- 



(a) Female sex-forms (macrogametocytes), with a very much 

 granulated protoplasm, which appears dark in colour. It takes on a 

 comparatively darker shade when stained. 



(b) Male sex- forms (microgametocytes), with a hyaline protoplasm, 

 pale in appearance, which stains a light colour. 



Among the structural peculiarities of Hcemoproteus noctuce, the 

 most conspicuous are the pigment granules enclosed in the plasm. 

 These are crystalline in structure and dark brown to black in colour ; 

 their presence renders the first finding of the parasites a comparatively 

 easy matter. They are the products of metabolism, and, for this 

 reason, are more numerous in the slow-growing gametocytes than in 

 the asexual forms. 



The pigment of Hcemoproteus, like that of the Plasmodia, is doubly 

 refractive and should be examined with the aid of a polarizing 

 apparatus. With a crossed Nicol's prism, the pigment granules 

 appear as bright points in the dark field. A very strong light upon 

 the object is essential. 



The nuclear structure should next be carefully studied. As in the 

 Trypanosomes, two nuclei are present. The one a large, loosely built, 

 principal nucleus, is situated in about the middle of the body, and 

 stains red with Geimsa's stain. The other, a much smaller structure, 

 staining violet with Giemsa, is placed close to the principal nucleus 



