442 C. CLIFFORD DOBELL. 



which they were living — I made some moist films in the 

 following way. The blood was spread in a thin film upon a 

 slide and immediately — without drying — exposed to osmic 

 vaponi- for about 30 seconds. The slide was then transferi'ed 

 immediately to absolute alcohol, where it was left to harden 

 for 15 minutes. After this treatment the Him was stained in 

 the usual way in Giemsa's stain — finally being allowed to 

 dry. I made several preparations in this way, and also by 

 the ordinary drying method with fixation in absolute alcohol. 

 In the preparations fixed with osmic vapour, both the blood- 

 corpuscles and Bacteria were beautifully preserved, and the 

 description of the organisms which follows is taken from 

 these preparations. 



The largest individuals of this form are of considerable size 

 (fio-s, 4-6, PI. 16). They attain a length of as much as 16 /i, 

 and a breadth of 2 fi. The cytoplasm contains no inclusions 

 and appears usually homogeneous, though occasionally it has 

 a slightly alveolar structure. In all the Giemsa preparations 

 the cytoplasm is coloured a bright blue (see figs. 1-20) — as I 

 did not extract the colour Avitli alcohol after staining. 



In all the organisms the chromatin is stained red — in sharp 

 •contrast with the cytoplasm (see figs. 1-20). It is distributed 

 through the cell in various ways, which can be classified 

 -conveniently into three main types of structure, with inter- 

 mediate conditions. 



The first type of nuclear structure is a typical spirogyra 

 form (figs. 1, 2, 4, 12). The nucleus is in the form of a spiral 

 or zig-zag filament, extending through the greater part of 

 the length of the cell. As in B. spirogyra, the filament 

 may be comparativeh^ straight (fig. 1) or much contorted 

 (fig. 2). All intermediate conditions occur. During division 

 the filament behaves in the same way as in B. spirogyra: 

 that is to say, it divides transversely into two, a half of the 

 ■original filament remaining in each daughter-cell (see fig. 2). 



The second type of nuclear structure is that shown in 

 figs. 3, 5-9. The organisms of this type show nuclei of very 

 irregular form. They possess chromatin structures in the 



