36 CORALS AND CORAL LSLANDS. 



the old tentacles, as illustrated in the following figure. It is not, 

 as is seen, a subdivision strictly into halves, as one carries off 

 the old mouth and stomach. The figure to the left represents 

 a polyp of the Astraea tribe, with already two mouths, through 

 a commencement of the process of subdivision. In the next 

 figure there are tentacles between the two mouths, so that each 



SPONTANEOUS KISSiON IN POLYPS. 



mouth has its own circle ; and in the third, the separation has 

 gone so far as to complete the circles and make two inde- 

 pendent polyps. This dividing one's self in two, for the sake 

 of an increase of population, is the process called spontaneous 

 fission or fissiparity. 



This mode of budding does not belong exclusively to coral 

 polyps, for it has been observed among a few Actiniae. Gosse 

 describes its occurrence in a British species, the Anthea cereus, 

 in which it results in two distinct animals. He says "the 

 fission begins at the margin of the disk, and gradually extends 

 downward until the separation is complete, when each moiety 

 soon closes and forms a perfect animal." The same author 

 alludes to the occurrence of double-disked individuals of the 

 genera Actinoloba, and Actinia as illustrating the process with- 

 out a separation of the spontaneously developed pair. 



This spontaneous fission is the conmion kind of budding in 

 the large Astraea tribe. 



The following figure represents a species of living coral of 

 the Astraea family, from the Feejees, the Astrcsa pallida, D. 

 which grew, and multiplied its polyps as it grew, by this 

 method. In such species some of the disks of the polyps will 



