ZOOLOGY: G. H. PARKER 
385 
THE EFFECTORS OF SEA-ANEMONES 
By G. H. Parker 
ZOOLOGICAL LABORATORY OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT 
HARVARD COLLEGE 
Received by the Academy, May 6. 1916 
Sea-anemones, like other animals, have special sets of organs, ef- 
fectors, by which they respond to changes in the environment. In 
these animals there are at least four sets of such organs: the mucous 
glands, the nematocysts, the cilia, and the muscles. 
The mucous glands are unicellular glands found on almost all surfaces 
of the body and concerned partly in protecting the surface against in- 
sult and partly in rendering it sticky whereby the animal as a whole 
adheres to a rock or other fixed object or foreign bodies adhere to the 
animal as in the collection of food by the tentacles. 
The nematocysts are the well-known organs of defense and offense. 
They are most numerous and best developed on the tentacles and on 
the acontia. By their abundant discharge large animals may be stung 
and driven away and small ones killed and appropriated for food. 
Cilia are means of generating currents and of transporting small 
bodies over surfaces and through tubes. They are best developed on 
the tentacles, the acontia, and the oesophagus. The oesophageal cilia 
ordinarily beat outward, but in the presence of food they reverse tem- 
porarily and beat inward thus carrying the food into the digestive 
cavity. 
The mucous glands, the nematocysts, and the cilia have all been sup- 
posed to be under nervous influence. In all cases their action in refer- 
ence to the stimulus appears to be strictly local; that is, they become 
active only over the exact region stimulated. Moreover if sea-anemones 
are subjected to anesthetics, such as chloretone, or magnesium sulphate, 
their nervous activitites can be completely aboHshed but without inter- 
fering in the least with the secretion of mucus, the activity of nemato- 
cysts or of cilia including their reversal. For these reasons it is conclud- 
ed that the three types of effectors just mentioned are independent of 
nervous control and respond to direct stimulation. 
Muscles on the other hand are commonly under the influence of 
nerves, an influence that disappears entirely when the sea-anemone 
is fully anesthetized. Some muscles, however, such as the longitudinal 
muscles of the acontia, have been shown to be independent effectors. 
They are slow in response often requiring a minute or more between the 
