312 THE MICROSCOPE. 
with the original Santa Monica Diatoms to determine whether it 
contains the same variety of forms. 
Dr. Riehl exhibited a pure culture of Staphylococcus pyogenes 
aureus; also, a stained and mounted specimen of the same. 
ZOOLOGY 
NOTE ON A PECULIAR HABIT OF HYDRA.* 
i September, while examining an aquarium containing 
Hydrodictyon, Spirogyra and other plants, Mr. W. G. Tight 
observed, on the sides of the glass, a few Hydras, and as some 
would be needed for his class work in November, he placed the 
vessel in a window and renewed the water from time to time. 
He noticed they were reproducing very rapidly by budding, but 
a short time before the class needed them they had all disap- 
peared. His first thought was that they had been disturbed, 
but upon accidentally turning over a piece of bark that was at 
the bottom of the vessel, he found beneath it all the animals that 
had but two days before been attached to the sides of the glass.. 
Upon examination he discovered that without exception they 
were all reproducing by means of eggs. The large ovaries and 
the testes, which were producing spermatozoa with two fla- 
gella, were forming from the ectoderm in numbers as high as six 
on asingle animal. By placing some of the Hydras in the light, 
they again began to reproduce by budding, showing that this 
reproductive method seems to take place in the light, while, 
when about to be reproduced by means of eggs the animal seeks 
the dark and becomes quite inactive. Yet it is possible in this 
case that a fall in the temperature of the room might account for 
the sudden change observed in the method of reproduction. The 
eggs, which are covered with a thick chitinous shell, fall to the 
bottom and pass the cold months apparently unchanged. The 
species under observation was Hydra fusca. 
T a late meeting of the London Zoological Society, Dr. H. 
Woodward exhibited a pearl mussel which had entombed a 
little crab (Pinnotheres) in a cyst of pearl. ‘‘ Whether or not,” 
said Dr. Woodward, “in this case the unlucky male intruded 
himself upon Meleagrina at an unfavorable period, and finding 
* Bulletin Denison University, IV., I., 131. 
