. Carnegie Institution of Washington publication. POSTLARVAL DEVELOPMENT. 63 containing Zooxanthellse, would at times be seen whirling round and round within the stomodaeum, and would afterwards be jerked out and lost to the polyp. Even after three months such extrusions would still take place. The young polyps varied much in their rate of growth, especially in the later stages ; indeed, in some instances, development seemed to be wholly arrested. The isolated polyps progressed most rapidly, but among these many differences were recognizable. The polyps forming colonies made scarcely any progr
. Carnegie Institution of Washington publication. POSTLARVAL DEVELOPMENT. 63 containing Zooxanthellse, would at times be seen whirling round and round within the stomodaeum, and would afterwards be jerked out and lost to the polyp. Even after three months such extrusions would still take place. The young polyps varied much in their rate of growth, especially in the later stages ; indeed, in some instances, development seemed to be wholly arrested. The isolated polyps progressed most rapidly, but among these many differences were recognizable. The polyps forming colonies made scarcely any progress after the first week or two. In the group represented in plate i, fig. 6, no increase beyond the six tentacles and twelve simple septa occurred up to six weeks, when the colony was preserved. The development of the various organs was characterized by certain well-marked intervals of rest and growth. A week or two might pass without any conspicuous change taking place, and then progress would be somewhat rapid. The order of appearance of the organs varied somewhat in dif- ferent individuals ; at first some organs of a system were developed a cycle at a time, and the remainder in successive pairs from one border of the polyp to the other. Perhaps under the artificial conditions the duration of some of the intervals was partly determined by the state of the water and the amount ^ ^ . ^ -^ ^ Fig. o.—Diagram snowing the course of the and character of the food supplied. Still, there circulation within the imemai cavity of a ^ - , . • • 11 larval polyp. were certam definite resting stages appearing m all the pol3'ps and seeming to possess a phylogenetic as well as an ontogenetic significance. The following were the most conspicuous phases of growth: Of the mesenteries the protocnemes were established at the time of settling of the larvae, and the six pairs are shown to develop in a regular consecutive manner \\4thout any marked intervals (p. 76). Four of the six bilateral pa
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