ON THE NEMATODES OF THE COMMON EAETHWORM. 637 
some not very apparent reason exceedingly short-lived. Had 
the conditions been more favourable, they could have been 
maintained through a much larger number of generations, 
and would have thrown more light on the sexual phenomena 
of the species. 
LjfFE-HlSTOEY. 
(1) Investigation of Problems relating to the 
Life-Cycle. 
It has been already shown that active and encysted larvae 
of Rhab ditis pellio B. infest the nephridia and the coelomic 
cavity of Lumbricus terrestris respectively. It is also 
known that these larvae, on the death and decay of the host in 
damp earth, become sexually mature and reproduce. Beyond 
this, except for a few scattered details mentioned in the litera- 
ture of the Nematoda, the course which events take in a 
natural state has not been known. It was in the hope of being 
able to elucidate some of the interesting questions which sug- 
gested themselves in connection with the life-history that 
certain experiments were undertaken. The difficulties were 
considerable. It was found exceedingly difficult to imitate 
experimentally the natural conditions under which the 
nematode and also the worm live. Both animals were at a 
disadvantage, and were often unable to develop in a normal 
manner or in many cases to grow or even to live at all. The 
results obtained from this investigation are, therefore, 
incomplete, and still leave room for further work. 
(1) The Nemat ode not confined to the Body of 
the Worm during the Latter’s Lifetime. — An 
experiment to determine whether the larval nematode ever 
leaves the worm while the latter is living was several times 
made. ALumb. terrestris was first thoroughly washed 
in order to remove any soil-nematodes which might be 
adhering to the outer surface of its body, and was then 
placed with filtered water in a watch-glass. The tail of the 
