the perforated coral chamber it maintains respiratory 

 and feeding currents, and when mature it is visited 

 by a minute male able to make its way through the 

 small openings in the coral. 



Sediments would clog the delicate ciliary-mucus 

 feeding apparatus of corals were they not constantly 

 removed by reversing the ciliary feeding currents to 

 carry foreign particles to the outer edge of the feed- 

 ing disk and drop them off. Some polyps simply 

 shake off sand by rising up in their little cups. De- 

 spite this steady grooming, rapidly settling sediments 

 in shallow waters seriously limit the distribution of 

 reef corals by smothering the little setding larvae and 

 by making the water too turbid to admit sufficient 

 light for the plantlike cells in adult tissues. 



The classification of corals cuts across such differ- 

 ences as solitary and colonial habit, distribution over 

 the seas, and whether or not the coral is an im- 

 portant reef-builder. It is based on the finer structure 

 of the skeleton. Since it is not possible here to take 

 up the many kinds of corals group by group, we shall 

 consider them in two categories which are convenient 

 for readers who live on temperate shores and which 

 do have real significance in the mode of life of the 

 corals. 



Corals Extending into Temperate or Cold Waters 



The solitary cup corals (Plate 23) and the tall 

 branching colonies considered here belong to groups 

 represented on tropical coral reefs and in deep tropi- 

 cal waters, but they are not restricted to such waters, 

 and many do best in subtropical or cool seas all 

 over the world. Nor are they limited to shallow wa- 

 ters, as reef corals are. Delicate branching forms 

 that occur at great depths in the tropics, even to 

 24,000 feet or more, can be dredged at lesser and 

 lesser depths as we move to cooler latitudes. Most of 

 these corals do not harbor the plantlike cells that play 

 so great a role in the life of reef corals, and they are 

 quite negative to light. Where they do not keep to 

 deep waters they grow in dim rock pools, on the un- 

 dersides of stones, or in the shade of neighboring 

 corals on a reef. The yellow, orange, red, brown, 

 and black pigments which color the soft tissues of 

 many may in bright situations help to screen the 

 strong light. 



The little orange-red solitary cup coral, Bcilano- 

 phyllia elegans, is abundant in shaded situations in 

 Monterey Bay in California and northward to Puget 

 Sound. When the delicate flesh is so tightly con- 

 tracted that it forms a mere veil over the hollowed 

 cup and its radiating ridges, it measures V4 to V2 of 

 an inch across. Fully expanded, the little polyp rises 

 much higher than the cup and extends long, tapering 

 transparent tentacles covered with wartlike batteries 

 of stinging cells. On southwestern British shores 

 Balanophyllia regia, with bright yellow warts on the 



tentacles, is called "the red and gold star coral." 

 Close to shore it is rare, but in deeper waters its cups 

 are found in great numbers. 



The "Devonshire cup coral," Caryophyllia smithi, 

 is found at low-tide mark in southwest England, and 

 is often dredged from the continental shelf south of 

 Ireland and at all depths in the English Channel, 

 where it attaches to rocky outcrops on the soft bot- 

 tom. The white or pinkish disk, about -54 of an inch 

 across, is ringed with chestnut brown around the 

 mouth; the transparent tentacles have brown mark- 

 ings and silvery white knobbed tips. On the Ameri- 

 can Pacific coast Caryophyllia is a shore form in 

 Puget Sound, and occurs deeper farther southward. 



A larger fan-shaped solitary coral, Flabellum, is 

 common on Mediterranean bottoms alongside Bal- 

 anophyllia, and also on deep mud bottoms in the 

 Atlantic. A salmon-colored species, about 4 inches 

 across, comes up in dredges from Newfoundland to 

 Florida. Flabellum is attached when young but later 

 may lie loose on the bottom or with the tapering 

 base imbedded in the mud. 



The "star coral" of American coasts is Astrangia, 

 which forms small encrusting colonies with closely 

 spaced cups. The knobbed tentacles, dotted with 

 warts of stinging cells, catch tiny crustaceans and 

 even minute fishes. Astrangia danae, with colonies 

 usually 2 or 3 inches across, has white or pinkish 

 polyps less than Vi of an inch high. It encrusts rocks 

 from Cape Cod to Florida. This is a hardy species, 

 and when brought in to an aquarium, even after be- 

 ing shipped hundreds of miles from the sea, it can be 

 maintained for some time on bits of raw meat. A spe- 

 cies in southern California, once said to be common 

 in pools near La Jolla, was described as orange or 

 coral red, with lighter tentacles ending in white 

 knobs. 



In deep Atlantic waters the tall, branching colo- 

 nial corals that dominate whole areas of the conti- 

 nental shelf, especially on its sloping edge, have large 

 blossom-like polyps that are widely spaced on the 

 shrublike or treelike branches. Dredging reveals 

 slopes of the northeastern Atlantic, from six hun- 

 dred to six thousand feet, where the bottom is 

 covered with open or dense thickets of yellow Madre- 

 pora and Lophelia. A species of Lophelia is even 

 better known from the deep Norwegian fjords, es- 

 pecially Trondheim Fjord, where at about six hun- 

 dred feet the rocky bottoms support great banks of 

 Lophelia and Amphihelia. These differ from typi- 

 cal coral reefs in that they never come to the surface. 

 Also scattered over the continental shelves and slopes 

 are great patches of Dendrophyllia. 



All these deep-water branching colonies are en- 

 crusted with small solitary corals and with some three 

 hundred species of other invertebrates that are fas- 

 tened permanently and grasp their food out of the wa- 



110] 



