[88 W. K. ALLKX. 



preliminary survey of the local held soon showed. Lack of better 

 material was therefore the principal reason for choo-ing Linniodri- 

 lits. Of points distinctly in its favor, tin- mo>t prominent were 

 accessibility, hardiness, adaptability to laboratory conditions 

 and rapidity of regeneration. ( )n the other hand, the small si/r, 

 irrital)ility, quickness and sandy food caused some serious dif- 

 ficulties. The specimen- n-ed \\ere taken fnun a -andy slouch 

 margin just north of I'rbana Fair Grounds. All were in good 

 condition and in a few hours appeared quite at home under 

 laboratory conditions. 



The effort was made to select 120 worms of equal median si/e, 

 but their activity was so great and their appearance changed so 

 quickly that the results showed considerable variation, ('.real 

 care was taken to make exact transverse cuts at the middle, but 

 here again, activity interfered and there was a con>idcrable 

 percentage of errors in cutting. For operation each worm \\as 

 placed on a paraffine block and a quick even cut was made- with 

 a sharp, thin scalpel. Anterior parts only were retained. Those 

 of the first five worms bisected were at once stupefied in weak 

 chloretone solution and killed in Gilson's sublimate mixture (Lee, 

 1900). All other worms were handled in the same way. The 

 second five was kept alive I hour after operation. All others 

 were placed in 10 cm. Petri dishes in which \\as about 4 c.c. of 

 sterilized native mud with 30 c.c. of tap water. Ten were placed 

 in each dish except by miscount due to disappearance in the 

 mud. Two dishes with unoperated worms were kept for check. 

 One hundred were bisected. \Yater was changed in the Petri 

 dishes twice daily immediately after taking the temperature of 

 the water already in the dishes. The highest temperature- re- 

 corded was 28 C., the lowest 21 C. The greatest duct ii.it ion 

 in 12 hours was 5. While it was unfortunate thai laboratory 

 conditions were not such as to permit more uniform tempera in re, 

 it is hardly probable that even this variation seriously affected 

 these hardy worms, none of which died. Li^ht and other con- 

 ditions were kept as nearly uniform as po-,>ible. 1 )iivci sunlight 

 was avoided altogether. 



As noted before the first five was killed immediaielv after 

 operation, the second in I hour, third in (> liour^. toiirth in 12 



