578 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



the larger. In fully established colonies the tentacles appear practically dicyclic, and are both 

 entocoelic and exocoelic in position; the former are the more internal, and correspond with the septa 

 below, while the exotentacles have no corresponding septum beneath. Usually the tentacles are 

 shortly conical, with a white opaque apical swelling, not forming a distinct knob; at other times 

 they .lie narrower, and more elongated, and the apex appears as a spheroidal knob. AVhite. oval 

 or irregular nematocyst batteries, varying in size and arranged circularly, occur all over the 

 surface. On full expansion the tentacular walls may become involved in the discal tissues, to such 

 an extent that they appear as mere circular patches, barely distinguishable except for the presence 

 of the denser apical region. Under certain conditions some of the tentacles have been found 

 completely introverted, oval apertures indicating their position externally: under these circum- 

 stances the disk appears as a smooth, naked, flattened expansion, not sharply marked off from 

 the column. 



The disk is verrucose. usually depressed, and ridged and grooved radiately, the grooves cor- 

 responding with the mesenteries. The radiating areas are larger and smaller, but the alternation 

 is not always regular; where the discal system is elongated the areas become more transverse. 

 Numerous oral apertures occur along the discal depressions, and vary much in size. Some may 

 have a longer diameter of 2.5 mm.; the smaller are circular, but others are oval, the greater 

 diameter being always along the larger discal axis. The mouths are usually open, allowing the 

 stomodseal wall to be seen, and often occur on a distinct raised peristome; when closed they 

 appear as mere slits in the disk. In the condition of partial expansion the apertures occur at 

 intervals of about half a centimeter, the number varying, of course, with the size of the colony. 



The stomodseum is sharply marked off from the disk, no rounded lips intervening; under 

 certain conditions it may be partly extruded. The walls are very deeply ridged, as many as 

 seven or eight, or even ten, ridges occurring on each side. They can be seen to correspond with 

 the line of attachment of the mesenteries on the internal side, and thus represent the number of 

 complete mesenteries associated with each stomodseum. 



During full expansion the polvpal tissues are semi-transparent, and the internal mesen- 

 teries can be seen through. In one ease seven pairs were found to reach the stomodseum, and in 

 another ten pairs; in one colony the numbers of perfect mesenteries around four oral apertures 

 were 12, 15, 17, and 20, respectively. The course of the mesenteries from the periphery towards 

 the stomodseum, as seen through the disk, is mostly at right angles to the calice wall. In some 

 pairs the course is curved, while in those most distant from the oral aperture it may form an 

 obtuse angle. The mesenteries are also seen extending the whole way down the edge-zone, as in 

 the column wall of an Actinian. 



The color is very variable, even in colonies living within the same area. Yellowish brown, 

 as in so many other corals, is the fundamental color, and upon this may be superposed an 

 ectodermal opaque white or green. The column wall generally exhibits only lighter and darker 

 shades of brown, due to the internal zooxanthellse; and sometimes the whole colony may be of this 

 character. The disk in most cases is lighter than the rest of the colony, often an opaque pale 

 green; the color here appears quite superficial, as if produced by some dense, opaque white or 

 pale green ectodermal deposit. The rows of verruc;e also may be opaque white, while the ground 

 color is green. A similar appearance, though somewhat less dense in character, may occur on 

 the upper region of the column wall. In numerous colonies at Bluefields the coloration was 

 distributed in darker and lighter irregular patches. When the polyps are fully distended, the 

 distinctive colors largely disappear, the tissues becoming a pile brown, and more or less trans- 

 parent. The tentacles are always colorless and transparent, but more opaque over the lateral 

 indicating areas, and entirely so at the apical swelling. A dull, white ring may surround the 

 oral cone. 



Colonies have been collected of which thi' gastro-ccelomic cavity contained numerous free 

 swimming larvse, readily seen through the partly transparent tissues. Many also circulated 

 freely within the tentacular cavities. Most id' the larva' were elongated, with a light broader 

 pole, directed forward in progression, and a dark brown, narrow, posterior pole. At times they 



