630 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Proliferating Cysticerci.* — Prof. M. Braun found in the axillary 
region of the zizel ( Spermophilus citillus) a large number of proliferating 
cysticerci, showing external posterior buds. By infecting three foxes he 
proved that these bladderworms were the cysticerci of Tsenia crassipes, 
and this was confirmed by some observations of Bremser and others, 
which a search into the literature brought to light. 
Echinoderma. 
How do Starfishes open Oysters P f — Dr. P. Scliiemenz calls atten- 
tion to a fact which ought to be well known, that enormous injury is 
caused by starfishes to the oyster beds. Oysters, as we know, can close 
their shells quite tightly, and an interesting question arises, how is a 
starfish able to exert sufficient force to open them ? Starfishes which 
attack oysters may be divided into two groups ; those of the first have 
conical shaped arms ; in the second group the arms are far from being 
so conical in shape, but they are more or less cylindrical. The former 
live in sandy, the latter in rocky places. As the starfish cannot get the 
prey into his stomach he sends his stomach into his prey, that is to say, 
he throws his stomach out like a proboscis, either wrapping it round 
or forcing it within the shell of his victim. This throwing out of 
the stomach has been often described. An example which the author 
gives will show how cleverly an Asterias can force his stomach through 
openings which appear little adapted for the purpose ; for example, one 
w r ould imagine that a sea urchin would be safe from the attacks of a 
starfish, but in the Naples Zoological Station a moderately large sea 
urchin was attacked by two starfishes, one on either side. One had 
thrown its stomach through the narrow places between the urchin’s 
spines until it reached the skin, which, together with the muscles that 
attach and move the spines it devoured, so that the spines by degrees 
fell off. For the second starfish a way had been prepared, and with its 
stomach it reached the mouth of the urchin through this ; in spite of 
the urchin’s strong teeth it inserted its proboscis and so sucked out its 
victim like an oyster. 
As to attacking molluscs, the starfish might take them by surprise, 
or it might beset the oyster so long that it would be compelled by 
hunger and want of air to open. It has been suggested that the star- 
fish might hypnotise the molluscs, or might make an opening in the 
shell with the help of a boring apparatus, or an acid. Or yet there is 
another possibility, that the starfish pours a poison over, or rather within 
the shell of its victim, whereby the muscular force of the latter is en- 
feebled and the shell is opened. There remains yet one more possibility, 
namely, that the shell is opened by force. The author’s own observa- 
tion leads him to think that this last is the method which is really 
adopted, and he proceeds to bring forward proof that the animal does 
actually possess sufficient strength for the purpose. Some experiments 
which were made show that the pulling power may be estimated at 
1350 grm. Experiments were made with a species of Venus, and it 
was found that a weight of 900 grm. is quite sufficient to open a Venus 
in, on an average, fifteen minutes. It hardly requires to be stated that 
* Zool. Anzeig., xix. (1896) pp. 417-20. 
t MT. Deutsch. Seefischver., xii. (1896) No. 6 ; translated in Journ. Marine Biol. 
Aesoc., iv. (1896), pp. 266-85 (9 figs.). 
