120 NOTES ON NEMAS 



sectors, these united elements then acting in opposition to the dorsal 

 sector, the two jaws thus developed becoming one dorsal and one 

 ventral. There is no evidence of such a transformation. 



INTRA VITAM COLOR REACTIONS IN NEMAS 



We have slowly come to have great confidence in the specificity of 

 certain physiological actions. The known cases of specificity are 

 relatively few, and have been discovered largely by accident. We 

 do not know the exact nature or cause of this specificity. We intro- 

 duce into an organism certain substances, and definite results follow; 

 about the only thing we know in the matter is that these definite re- 

 sults follow with certainty. What the reactions are that bring about 

 the result we do not know. Our ignorance is so great that even our 

 theories are very vague. In such cases, if only we could see what it 

 is that happens while it is happening, it seems certain that important 

 advances would be made in our knowledge of nutrition, growth, and 

 decay, of physiology, pathology and medicine. 



If substances giving color reactions in living tissues could be applied 

 to small, transparent, varied and highly complex living organisms, 

 under circumstances that would permit microscopic examination while 

 the reactions are in progress, we might hope for more light on this 

 exceedingly important subject. Experiments I have made lead to 

 the belief that many of the conditions requisite for success in this 

 line of investigation can be much better realized than hitherto by 

 feeding colored substances, notably coal-tar dyes, to free-living 

 nematodes. 



These minute, transparent animals are comparatively highly organ- 

 ized; not only this, but also extremely varied in their habitats and 

 mode of life. Some are exclusively vegetarian, others exclusively 

 carnivorous, and others omnivorous. They constitute a group com- 

 posed probably of hundreds of thousands of species, embodying an 

 almost inconceivable number of kinds of physiological action. Their 

 organs are enclosed in a thin transparent cuticle, and are strung out 

 so as to make them unusually suitable for intra vitam examination. 

 Under slight pressure the nema flattens out more or less without losing 

 its vitality sufficiently to preclude satisfactory intra vitam exami- 

 nation under the highest powers of the microscope. 



