20 SCIENCE PROGRESS 



such conditions. It is very unlikely that the minute cocoons, 

 if inadvertently swallowed, would hatch out their young in the 

 human stomach ; or that the worms if swallowed unwittingly 

 with a salad would pass through the entire body and be 

 evacuated in a perfectly whole and sound condition. They 

 are so tender, and so utterly destitute of integuments of an 

 enduring nature, that they could not survive so severe an ordeal. 



(iv) The worms which have been submitted to me belonged 

 to the white-blooded group. The genera Fridericia and 

 Enchytraeus are rarely if ever found under such conditions 

 as would render us liable to swallow them in our food or drink 

 them in our water. They might be found in earth around 

 radishes, onions, or other salads, or even find their way into 

 minute crevices and disease spots, and so by a very rare chance 

 be eaten, if the usual care was not taken in washing them ; 

 but I cannot conceive of their finding a way into the human 

 body by any other means. 



(v) The Pachydrilids most frequently met with are not 

 usually less than £ inch in length. Should they, therefore, 

 find their way into our drinking water, their size and colour 

 would render them sufficiently conspicuous for the most 

 casual observer to discover them. But even in the event of 

 their being accidentally swallowed when a draught of water 

 is hurriedly taken, the softness of their bodies, and the absence 

 of all weapons of offence and defence, such as suckers, forceps, 

 and horny jaws, would render them perfectly innocuous. 



We may certainly conclude, therefore, that Pachydrilids 

 are never harmful to man, whatever may be their role as the 

 carriers of disease to other animals. 



Their Beneficent Action. — On the other hand it is equally 

 certain that their role is, on the whole, a beneficent one. In the 

 first place, feeding as they do on decaying vegetable and animal 

 matter, they greatly aid in the disintegration of material 

 which might easily prove dangerous. Thus they prepare the 

 way for bacteria and other lowly forms of life, aid the chemical 

 processes which are in action, and convert dead matter into 

 a rich and valuable humus. In mud and slime they help 

 by their movements to carry on oxygenation so that larger 

 forms of life may be able to exist. In sewage works they are 

 equally serviceable, and may possibly do much to keep in check 

 disease germs and injurious bacteria ; while their abundance 





