NOTES ON THE FREE-LIVING NEMATODES. 445 



The iusignificant development of glandular cells (which 

 ai*e found only in the CBSophagns) may be cited against an 

 intra-intestinal digestion of the bacteria, and whatever else 

 its significance may be, the chitinous layer which lines the 

 aliraentai'y canal throughout must prevent an ingestion of 

 bficteria by the endoderm cells themselves in such a way as 

 Colpidium preys upon the bacteria of the soil. 



Besides peptone solutions other culture media have been 

 used in the course of experiment. It was found possible to 

 raise two or three successive generations in a saturated solu- 

 tion of gelatin in water, and free-living nematodes matured 

 from the egg in solutions of amides like tyrosin and leucin, 

 but in these cases the growth was so much retarded and the 

 production of fertile eggs so curtailed that only pejitoue 

 solutions were used for extended experiments. 



The temperature at which the cultures were kept varied 

 from about 18^ C. in the summer to 12° C. in the winter, 

 though at one period it fell within three or four degrees of 

 zero. The effect of a temperature approaching freezing-point 

 was very marked, and showed itself in the almost entire 

 suspension of growth. Sterility was not induced, but only a 

 very few eggs were laid every day. 



Experiments were also made to find the highest tempera- 

 tures under which life and reproduction could continue. The 

 cultures Avere placed in a water-bath which could be kept 

 down to 25—30° C. Several individuals of the sixth genera- 

 tion were isolated with the temperature of the bath at 26° C, 

 going up to 28° C. One of these laid forty-three eggs on 

 September 8th. By September lltli these had developed 

 into hermaphrodites of mature size, but although they lived 

 for several days and were apparently in a quite healthy con- 

 dition, they never produced mature eggs or spermatozoa. 

 The ovary was distinctly seen with small nuclei, but there was 

 no aggregation of yolk. Changes of this kind occurred in the 

 other cultures. 



In addition individuals just ready to lay eggs were isolated 

 from the cultures at the temperature of the room and placed 



