NON-PROTOZOAN FAUNA OF SOIL 345 



Finely cut agar (3.5 grams) is soaked over night in tap water; excess of water 

 is poured off and agar is dissolved in 200 cc. of tap water containing 1.3 grams 

 of NaCl. The agar is neutralized and filtered; 1.6 grams of powdered brown 

 sugar or malt sugar is then added, the agar is sterilized and distributed into sterile 

 Petri dishes. The soil is inoculated, in the form of a fine layer, over the centre 

 of the plate. The living worms will move away from the soil and, after 24 hours, 

 they will be found on the clear agar about 0.5 cm. away. These worms, es- 

 pecially those bearing eggs, can be transferred to fresh agar plates, for the prep- 

 aration of pure cultures. 



FLAT WORMS (PLATHELMINTHES) 



The Turbellaria or free living flatworms are represented in the soil 

 by various species of Rhabdocoelae, Allocoelae and land Planarians. 

 Over thirty species of Rhabdocoelae were isolated from the soil. 5 

 Among the various genera found in the soil, it is sufficient to mention 

 Archivortex, Ade?ioplea, Acrochordonoposita, Geocentrophora, Prorhyn- 

 chus (P. stagnalis) and Planaria. The soil forms feed largely on 

 diatoms, rotatorians, tardigrads, oligochaetes, upon one another and 

 especially upon soil nematodes. 



The Trematoda are represented in the soil by the larvae of different 

 river flukes. 



NEMATODA 



Adult nematodes are usually cylindrical or spindle shaped, the pos- 

 terior end being often acutely pointed or modified in form. They are 

 transparent, non-segmented organisms, 20 to 100 times or more as 

 long as wide. When alive and active, they thrash about in pure liquid 

 without making much progress. They do not change their length 

 appreciably, being thus distinguished from earthworms and other 

 elongated small organisms, which change their length while moving. 

 Dead nematodes lie outstretched or in a slightly curved condition. 



Nematodes are found in all soils under different conditions, largely 

 in the upper 6-8 inches, although they are often abundant even at 

 lower depths 6 (No. 144, PI. XVIII). They can adjust themselves to 



Further information on the artificial cultivation of free-living nematodes is 

 given by H. Metcalf in Trans. Amer. Micr. Soc, 24: 89-102. 1903; and A. C. 

 Chandler in Science, N. S., 60: August 29, 1924. 



s Reisinger, E. Turbellaria. Strudelwiirmer. L. 6, T. 4, Schulze's Bio- 

 logie der Tiere Deutchlands. Borntraeger. 1923. 



6 Godfrey, G. H. The depth distribution of the root-knot nematode, Heter- 

 odera radicicola, in Florida soils. Jour. Agr. Res., 29: 93-98. 1924. 



