1 74 Phylum N emathelminthes 



the year from a corner grocery by asking for bulk cider vinegar. It will 

 live indefinitely in the laboratory if transferred to fresh vinegar every 

 two weeks. Since it is viviparous and transparent, all stages of develop- 

 ment may be examined in utero. Anatomical details, such as the ali- 

 mentary tract, nerve ring, spicules and sperms of male, uterus and 

 uterine development in female, and all young and intermediate stages 

 can be seen with a 4 mm. objective. Placed in a well slide and projected 

 on a daylight screen with a micro-projector, many anatomical features 

 may be shown on the screen under suitable magnification. 



M. E. D. 



ARTIFICIAL CULTIVATION OF FREE-LIVING NEMATODES* 



Asa C. Chandler, Rice Institute 



THE free-living nematodes of soil and of water may be studied to 

 great advantage by culturing them on ordinary nutrient agar plates. 

 A single isolated adult female of Rhabditis sp., placed on an agar plate 

 with a drop or two of dirty water to supply a bacterial growth, in a period 

 of 5 days will produce thousands of offspring which swarm all over the 

 plate. In 10 days the offspring will number many thousands, — males, 

 females, eggs, and young in all stages of development. 



For class demonstration of soil nematodes, a student may place a 

 small quantity of soil, preferably manured soil, in a piece of gauze or in 

 a fine sieve, and wash it in a beaker of warm water; in a few minutes 

 the majority of the nematodes present will have fallen to the bottom of 

 the beaker. If a drop or two of water from the bottom of the beaker is 

 then placed on the surface of a nutrient agar plate, and the plate covered 

 and left at room temperature for from 5 to 10 days, an enormous number 

 of nematodes of several species will usually be found. The majority of 

 the individuals move about on the surface of the agar, but some burrow 

 into it also. The movements on the agar are sufficiently impeded so that 

 they may be watched after the fashion of a slow-moving picture. The 

 swallowing of bacteria and fungus spores, the excretion of waste matter 

 from the anus, and every detail of locomotion may be observed under 

 ideal conditions. Species of Rhabditis and Cephalobus, and others not 

 positively identified, have been cultured in this manner. The method 

 suggests a great range of possibilities in the way of study and experi- 

 mentation, e.g., on foods, effects of hydrogen-ion concentrations and of 

 chemical substances, resistance to desiccation, tropisms, effects of various 

 modifications in environment on rate of reproduction and development, 

 etc. The extremely rapid rate of reproduction and ready inbreeding also 

 suggests possibilities in genetic experiments. 



♦Recast of article in Science 60:203, 1924. 



