146 Dr. J. E. Duerden on the 



formed only a single system. At the low scale of magnifica- 

 tion at wljich the section was drawn, most of the details could 

 be only diagrammatically displayed ; two stomodaja are 

 present, and with each is associated nearly the same number 

 of mesenteries as occurs in ordinary polyps, including two 

 pairs of directive mesenteries. The plane of fission is included 

 within the entocoeleof two opposite mesenterial pairs. Mani- 

 festly, if the two daughter polyps were to become completely 

 separated from one another, they would differ in no material 

 respect from one of the ordinary polyps of Cladocora, produced 

 in the usual manner by budding, or directly from the larva. 

 The cyclical hexameral plan of the mesenteries would be 

 preserved, and two pairs of directives would be present in 

 each. 



The mesenterial conditions represented by fig. 2 {^-d) are 

 clearly stages toward the establisiiment of a double series of 

 mesenteries, including also two additional pairs of directives. 

 "Whtn this is reached, fission of the stomoda^um takes place, 

 and practically half the total mesenteries, along with two 

 pairs of directives, are associated with each moiety. 



The results attained by simple fission in Cladocora are thus 

 the same as in Madtepvia and Pontes. The two moieties 

 are to all intents and purposes new individual polyps, corre- 

 sponding in every way with polyps originating as buds or 

 from larvffi. 



Though not quite so complete, similar results have been 

 obtained from the enlarged polyps on colonies of Stephano^ 

 coenia inttrsfpta (Esper), Svlenastrcea hyades (Dana), and 

 OcuUrta di^uaa, Lamarck. On any colony of Stephanocoenia 

 inters* pta most of the polyps contain only six complete pairs 

 of mesenteries and six ahernating incomplete pairs, forming 

 two cycles, as shown in fig. 4 a. In fig. 4 (h-d) the mesen- 

 teriiil plan of three enlarged polyps is represented diagram- 

 matically. In these many new n)esenteries have been added, 

 yet without increasing the number of cycles ; the mesenteries 

 throughout are in complete and incomj lete alternating pairs, 

 excejjt in one or two places where an incomplete pair is 

 wanting. Among the new pairs of mesenteries an additional 

 pair of directives (D) has appeared in each case. On 

 macerated coralla the septa are also arranged in two alter- 

 nating cycles, larger and smaller, alike in both normal and 

 enlarged corallites. 



Amongst the preserved material of S. intersepta at present 

 available, 1 can find lio example of an actual bioral polyp, or 

 of one undergoing fission. The characteristics of the enlarged 

 polyps, however, are so closely comparable with those of 



