CORALS FROM FUNAFUTI. 33 



there is a distinct calycular fossa, but, excepting in the largest 

 specimen, the septa scarcely project above the surface of the 

 disc, and their upper edges give evidence of their having been 

 recently severed across. 



The flat discoid shape of these young corals and the presence 

 of a large scar of detachment on their upper as well as on their 

 lower faces show that they are not pedicellate forms that have 

 simply been detached at the base, as is the case in several 

 species of Flahellum, but that they must have formed by the 

 transverse division of a fixed nurse-stock, just as the ephyrse 

 of Aurelia are formed from a strobila. Such a process of 

 strobilization is extremely rare in corals, but it has been 

 described by Semper * in Flahellum variahile. It is not exactly 

 the same thing as the formation of anthocyathi from the tropho- 

 zooid of Fungia ; for in the latter case the margins of the 

 calycle of the trophozooid expand laterally to form a broad 

 disc-shaped Anthocyathas before detachment takes place. The 

 theca of the Anthocyathus is on the lower surface, and the scar 

 of detachment is small relatively to the diameter of the Antho- 

 cyathus itself. After the first Anthocyathus is detached a new 

 one is formed by the upgrowth and subsequent outgrowth of the 

 septa within the scar at the upper end of the trophozooid, aud 

 this is in turn detached, the process being repeated three or four 

 times, but not more so far as is known. In Trochocyathus 

 hastatus the thecal walls of each disc-shaped young specimen are 

 nearly vertical, and the scar of detachment is nearly as large 

 as the disc itself. Moreover, it is clear that the young forms 

 are not successively completed and then detached, as in Fungia, 

 but that a number of young forms are segmented off from 

 the trophozooid, either simultaneously or in rapid succession, 

 before the septa have time to grow or to repair their divided 

 edges. 



The smallest of the three specimens from Funafuti appears to 

 be the most recently detached of the three. It measures rather 

 less than 3 mm. in diameter and 1 mm. in thickness. The 

 upper and lower surfaces are flat, and the margin of the disc 

 constituting the theca is evenly rounded and marked with 

 thirty-six costse, haviug the form of low ridges (PI. 6. fig. 8). 

 Six of these costse are somewhat more prominent than the rest, 



* Zeitschrift fiir wissenschaftliche Zoologie, Bd. xsii. p. 235. 

 LINN. JOURN. ZOOLOGY, VOL. XXIX. 3 



