156 J. J. LISTER. 



which the rings of charaberlets numbered from seventeen to 

 thirty-eight, there are eighteen whose primordial chamber 

 still contains a single nucleus. The nucleus measures about 

 24 X 14 /A, it is of a round or oval shape, and a close reticulum 

 can be detected in the interior. I have not seen definite 

 nucleoli, but the central region of the nucleus often appears, in 

 sections, to be separated from the peripheral region by a ring 

 of more deeply stained particles (figs. 47 and 48). 



In one specimen, with twenty-two rings of chamberlets, two 

 rounded nuclei are present in the primordial chamber. In several 

 others (fig. 49) no nucleus of the form above described is to be 

 seen, but in its place, numbers of compact bodies of different 

 sizes, and often of irregular shape, are present. These are not 

 confined to the primordial chamber, but extend into the circum- 

 ambient chamber and surrounding chamberlets. It would 

 appear that in the megalospheric form of this species, after the 

 individual has nearly completed its growth the nucleus breaks 

 up into a number of fragments, which become dispersed among 

 the chambers. 



Dr Hickson's collection from Celebes consisted of 117 

 specimens. They were obtained from the reef at Talisse Island, 

 to the north of the main island. Although, in this species, the 

 central chambers are not covered by those that are added later, 

 they are frequently obscured by a calcareous deposit on the 

 surface. By dissolving the superficial parts of the shell, the 

 central chambers may be exposed and their character re- 

 cognised. In some cases, however, the central chambers are 

 empty, and their character can then only be observed by- 

 examining the delicate organic basis of their walls. I failed 

 to recognise the character of the central chambers in two cases, 

 but of the remaining specimens only one belonged to the 

 microspheric form, the others being megalospheric. The size 

 attained by shells of the megalospheric form is much larger 

 than in those which I have seen from Fiji or Tonga. In one 

 case there ai-e as many as sixty-six rings of chamberlets be- 

 tween the primitive disc and the periphery. In sections of 



