I 
GEROULD : CAUDINA. 9 
I gladly take this opportunity to express a deep-felt gratitude to 
Dr. Mark for the invaluable assistance which he has rendered me 
during the prosecution of these studies. I would likewise make 
grateful acknowledgment of the kindness of Mr. Alexander Agassiz 
in permitting me to make use of the specimens of Holothuroidea 
collected in the expedition of the U. S. Steamer “ Blake.” I am 
also much indebted to J. S. Morris, M. D., of Revere, Mass., for 
valuable aid which he has given me in collecting material for study. 
Regarding vnethods, I would first call attention to the use of 
magnesium sulphate as a stupefying reagent. It was first recom¬ 
mended, I believe, by Tullberg (’91), and its action has recently 
been more fully described by Redenbaugh (’95). The use of a 
stupefying reagent in the preservation of holothurians in an ex¬ 
panded condition being imperative, I have given this salt a thorough 
trial, and have found it entirely satisfactory for the purpose. The 
method which I have employed is as follows: A specimen of 
Caudina is first allowed to become well expanded in a small quantity 
of sea-water, and then crystals of magnesium sulphate are added, a 
small teaspoonful at a time. If contraction occurs, the salt is 
added more slowly or the use of it is suspended entirely until the 
animal again expands. 
Perenyi’s fluid gave better general results in killing than any of 
the other reagents which were employed. Corrosive sublimate was 
found to be the most satisfactory in the preservation of the ovaries. 
Previous to embedding an object in paraffine it was often found 
necessary to remove bubbles of carbon di-oxide, which had gathered 
in the tissues during decalcification. This was accomplished, as 
suggested by Cu6not (’91), by placing the specimen under the 
receiver of an air-pump and exhausting the air. For staining on 
the slide nothing was found to surpass Ehrlich’s haematoxylin 
followed by eosin. Biondi’s triple stain — acidfuchsin, methyl green, 
and orange — was used with excellent success in studying the 
development of the zona radiata and other phenomena in oogenesis. 
For demonstrating outlines of epithelial cells a one per cent solution 
of silver nitrate was successfully employed, after washing the fresh 
tissue thoroughly with distilled water. 
It may be of interest to add that I have given the rapid method of 
Golgi what I believe to be a thorough trial, but without the slightest 
success. For weeks at a time I have experimented with it, treating 
tentacles and other parts of the body according to the well-known 
