692 SUMMARY OF CURRENT RESEARCHES RELATING TO 
must be taken to avoid contortion, or an excessive discharge of mucus 
from the gland-cells of the epidermis. Seventy per cent, alcohol was 
used, and it was made to drop on the filter-paper at the rate of sixty 
drops a minute. This is a modification of the method suggested in 
1890 by Cerfontaine. In about an hour the worms are so stupefied by 
this method that all the paper may be removed except the small piece 
on which the alcohol drops, and the alcohol may be made to drop more 
rapidly. At the end of two hours the worms were placed in 50 per 
cent, alcohol for an hour, in 70 per cent, alcohol for 24 hours, in 96 per 
cent, alcohol for the same time, and they were then preserved in fresh 
alcohol of the same strength. Parts of worms chosen for study were 
run through absolute alcohol, cedar oil, soft paraffin, one half hard and 
one half soft paraffin, and finally imbedded in the last. Each change 
from one reagent to another must be made gradually, and the temperature 
of the paraffin bath must not rise above 54°. The minute structure 
of the sense-organ did not show well in sections more than 10 /x thick. 
Dr. Huber suggested to the writer two changes in the published method 
of using silver nitrate. The first was to leave the turpentine for 15 
minutes instead of five, and the second was to use pure balsam instead of 
turpentine balsam. 
Examination of the Spermatozoa of Echinoderms.* — Prof. G-. W. 
Field very rightly thinks that, owing to the extreme delicacy of the 
cells involved, and the extraordinary distortion caused by most killing 
fluids in common use for other tissues, he should report with great care 
the methods which he found best adapted for his examination of the sper- 
matozoa of Echinoderms. Dealing first with fresh material on the 
slide, he describes the use of neutral dahlia and methyl-green. To a 
watchglassful of sea-water add a small quantity of concentrated aqueous 
solution of dahlia, filter very carefully several times. Place the living 
spermatozoa in a drop of this liquid on the slide. After three minutes, 
add a drop of a dilute solution of methyl-green prepared in the same 
way. This method gives a minimum distortion, but unfortunately the 
results are very transitory. The value of this method lies in its delicacy, 
and for that reason very clean and very dilute, as well as freshly pre- 
pared, stains are necessary. A very weak solution of tincture of iodine 
in sea-water, very carefully filtered, preserves the shape and size very 
well. The author found that a method which was remarkably good for 
use in studying the mode of formation of the tail of the spermatozoa, 
was to take a 10 per cent, solution of chloride of manganese, and add 
to it a concentrated aqueous solution of dahlia ; acetic acid combined with 
dahlia and methyl-green gave fair results. Osmic acid was found very 
useful for demonstrating the centrosome. 
Prolonged fixation was found to be valuable for studying the details 
of the development of the spermatozoa. A piece of the testis was teased 
in a small quantity of water, fixed in Flemming’s chrom-osm-acetic for 
24 hours, then washed for 24 hours or more in distilled water, frequently 
changed and shaken. After, treat with some aqueous stain ; the moun- 
ting may be made in dilute glycerin or in dammar. The cells become 
separated by tapping the cover-glass gently with the point of a needle. 
Journ. Morphol., xi. (1895) pp. 238-41. 
