416 H. BOSCHMA. 



struggling movements cause a number of neighboring tentacles to 

 move towards them, so that they finally become completely 

 enveloped in a number of tentacles. Then they are slowly trans- 

 ferred to the mouth in the above described way, but they often 

 remain struggling heavily, even when going down the stomo- 

 dseum. Usually, however, the tentacles keep these larger organ- 

 isms in the same position for some time, and only after they have 

 ceased to struggle they are transferred to the mouth. 



These experiments with copepods and other small crustaceans 

 show that the tentacles instantly react when they are touched by 

 a free swimming animal. The oral disk on the contrary is quite 

 indifferent to the contact of these planktonic organisms. Some- 

 times a small floating copepod may be seen sinking down and 

 falling on the oral disk of a coral polyp. It can remain there for 

 some time without calling forth any reaction of the polyp. 

 Afterwards it can swim away unharmed unless it happens to 

 touch one of the tentacles, in which case it immediately brings 

 forth the capturing reactions of the tentacle. 



In the case of the feeding experiments with crab meat or other 

 non-moving material of food the movements of the tentacles are 

 very slow. In expanded polyps the small morsels of meat 

 strongly adhere to the tentacles to which it is offered, and usually 

 some neighboring tentacles also bend towards the meat, more or 

 less enveloping it. The mouth with the top of the conically 

 expanded central part of the oral disk moves slowly towards the 

 prey and the tentacles push the meat downwards into the 

 stomodseum. Some tentacles often protrude into the stomo- 

 daeum, pushing against the food-material. The mouth then 

 closes and the food slowly passes down into the gastric cavity. 



Generally after the feeding the polyps partly expand by raising 

 their column often considerably above the skeleton. The tenta- 

 cles also remain in a more or less expanded condition. This 

 expansion of the polyps generally takes place as well after the 

 feeding of meat as after the feeding of free-swimming organisms. 

 In this state the polyps are almost indifferent to mechanical 

 stimuli. Whilst a hungry polyp quickly contracts when gently 

 touched by a forceps the polyps which have just fed do not react 

 on the same stimulus. A further peculiarity is that often some 



