SOIL PROTOZOA. 311 



liquid ; and in order to obtain these forms, coverslips were floated 

 on the surface and placed on the bottom. In other cases the vatt 

 majority of the organisms occurred about midway in the depth of 

 the culture, and in order to obtain coverslip-preparations of these 

 I drew out small quantities of the culture where the protozoa were 

 thickest by means of a fine pipette, and then made smears with 

 the liquid. As a rule, three cultures were made from each soil, 

 in order to obtain a representative fauna, and the cultuies were 

 examined for several days to note sluj succession of forms. Cover- 

 slip-preparations were fixed in Maier"s solution or in Bouin's 

 fixative, and iron-htematoxylin was used as the stain throughout ; 

 occasionally preparations were counteistained with lichtgriin- 

 picric. 



I propose in the following pages to deal with the protozoa 

 encountered imder the heading of the group to which they belong, 

 mentioning the particular soil or soils from which they wei-e 

 taken. 



A. Flagellata. 



(1) Prowazekia (Bodo) salta>s Ebrbg. (PI. I.) 



In one of my cultures of Barnfield 1870 soil a very small 

 jumping flagellate occurred in abundance at the bottom of the 

 liquid. It appeared somewhat bean-shaped when seen under a 

 low power, and I at once concluded that it was Bodo saltans. A 

 coverslip-preparation was made, and on it I obtained many 

 dividing organisms, from a study of which I have been able to 

 work out fairly completely the process of nuclear division. I will 

 describe the structure of a normal organism, and then deal with 

 the question of identification and nomenclature. 



(a) Structure. 



The body is somewhat bean-shaped and is oval or round in 

 cross-section. Been from the ventral aspect — i. e. the side on which 

 the flagella arise (fig. 1) — the anterior end appears flattened and 

 is turned towards the left, where it terminates in an almost 

 straight edge. This anterior portion of the organism is really an 

 extension of the dorsal region, and is separated on the vential 

 surface from the main part of the body by a considerable depres- 

 sion, in which the mouth is situated. Fig. 2 shows a side-view 

 and the relations of the anterior end to the depression, etc. 



The trophonucleus is generally found towards the left side of 

 the body when the organism is viewed from the ventral surface. 

 It consists of a central deeply staining karyosome, which is con- 

 nected witli the nuclear membrane by means of sti-ands which 

 stretch across the extra-karyosomic zone; and at their insei'tion 

 on the membrane produce slight thickenings. 



The kinetonucleus is an irregular granular mass, often some- 

 what triangular in outline, and, on the whole, stains less intensel v 



21* 



