No. 2.] THE MORPHOLOGY OF DERO VAGA. TA] 
body is constant, z.e., only enough are regenerated to complete 
the five first segments. If two segments are removed a like 
number will be regenerated, but if seven segments be removed 
there will be but five new segments formed. In the latter case 
the regeneration proceeds much more slowly than in cases 
where fewer segments are removed. In order that the removed 
anterior portion of a worm regenerate a tail it seems to be 
necessary for it to have at least three or four segments in 
addition to the five in the cephalized part. 
In case a cut is made a short distance in front of a fission 
zone the part anterior to the zone may disintegrate while the 
posterior individual continues to live, and the normal process of 
regeneration is apparently hastened to adjust the worm to the 
new conditions. 
3. METHODS. 
The following methods were found to give good results: 
Killing and Hardening. — Hot corrosive sublimate (saturated 
aqueous solution); hot acetic corrosive sublimate, Hermann’s 
fluid, and 1/10% osmic acid. 
Maceration. — 1/10% nitric acid, also a mixture of glycerine, 
acetic acid, and water, equal parts. The worms treated with 
the nitric acid were dissected with needles ground flat. 
Staining. — Of the ordinary stains Delafield’s haematoxylin, 
Bohmer’s haematoxylin, Grenacher’s borax carmine, and the 
triple stain of Heidenhain-Biondi-Erlichi gave good results. 
For the working out of the nervous system and sense organs 
the following methods were used: 
Gold Chloride. —The method employed was essentially the 
same as that given by Mr. C. L. Bristol in the American Natu- 
ralist for September, 1894. The live worms were killed in 
10% formic acid and left for one minute, after which they were 
placed in 1% aqueous solution of gold chloride for ten minutes, 
and then left in 1% formic acid for from two to four hours. 
The gold chloride solution was kept out of bright sunlight 
while the specimens remained in it. The reduction in 1% 
formic acid was carried on for a portion of the time in 
sunlight. 
