222 
BULLETIN OF THE BUREAU OF FISHERIES. 
MATERIALS TESTED. 
These consisted of samples of a coal tar creosote and of five fractions obtained 
by the redistillation of another coal tar creosote. The two creosotes, however, 
were similar in grade and composition. In Table I are given the properties of the 
creosote and of the several fractions. These materials and the data on them were 
furnished by the Forest Products Laboratory. Other poisons tested were a series 
of light oils, a series of tar acids, a series of tar bases, and a series of solid aromatic 
hydrocarbons. 
Table I . — Properties of creosote and fractions. 
LIMNORIA. 
Limnoria is a very small marine crustacean, 2 to 3 mm. in length and 1 to 1 \ 
mm. in width. Limnoria attacks unprotected wood in great 'numbers. Although 
not as destructive as the shipworms proper, it is, nevertheless, of considerable 
economic importance. A short description of this animal is given to make clear 
the criteria of toxicity which were used. 
The body of Limnoria consists of a number of consecutive joints or segments 
which are movably articulated together. The body is divided into three parts: 
A head, a thorax composed of seven segments, and an abdomen of six segments. 
Each of the thoracic and abdominal segments is provided with a pair of legs. At- 
tached to the abdomen is a series of extremely thin leaflets — the swimmerets. The 
latter are respiratory as well as natatory in function. In the normal animal, 
whether it is quietly burrowing or crawling around, these swimmerets are in con- 
stant, rhythmic motion. The body of the borer is covered by a very thin translu- 
cent, chitinous shell. 
EXPERIMENTAL METHOD AND CRITERIA OF TOXICITY. 
The usual experimental procedure was as follows : About 25 Limnoria, freshly 
obtained frdm unprotected wood, were transferred with some sea water to each of 
five Stender dishes. In all but three experiments there were five experimental 
periods, so that about 125 Limnoria were used in each experiment. No animal 
was used more than once. Just before the addition of the toxic preparation — 
ordinarily 25 cc. — the sea water was drawn off as completely as possible with a 
capillary pipette. As soon as the animals became paralyzed, they were distrib- 
uted as evenly as possible over the bottom of the dish. If the time in the poison 
