THE ANATOMY OF THE MADREPORARIA. 29 



sides in a manner more characteristic of certain Alcyonaria, so that 

 in transverse sections of the colony they frequently appear to lie 

 free in the coelenteron. Two stages in the development of the 

 spermatozoa are figured as well as the preservation of the material 

 would allow (Figs. 14, 15). 



In both this and Seriatopora there was left, after decalcification, a 

 residue in the position occupied by the corallum, which, though 

 staining faintly both with hsematoxylin and with borax carmine, 

 showed no distinctly organic structure. 



In transverse sections of the polyps it is just possible to detect, at 

 the point of the insertion of the mesenteries in the corallum, structures 

 similar to those described by Sclater (11) as calycoblasts. Their 

 excessive minuteness in Pocillopora rendered an accurate investiga- 

 tion impossible, but they certainly appeared to me to be rather 

 connected with the attachment of the mesentery to the corallum than 

 with the secretion of coral. 



Milne-Edwards and Haime, "Hist. Nat. des Corall.," iii., p. 301, 

 pi. F 4, figs. 1, 2. 



Agassiz, "Nat. Hist. United States," iv., 295, pi. xv., 14. 



Klunzinger, " Korallthiere Eoth. Meer.," ii., 66, pis. vii., viii. 



Note on the Skeleton of Flabellum. 



In his latest addition to the literature of the subject (9), the main 

 part of which I do not propose at present to discuss, Dr. von Koch 

 treats, amongst others, of the skeleton of Flabellum. 



1. He states that the dark line of growth visible in transverse 

 sections of the calyx, which indicates the earliest formed part of the 

 coral at that level, is in Flabellum placed peripherally (Fig. 16), and 

 consequently that the skeleton is laid down from without inwards. 



2. Elsewhere in the same paper he infers, from his researches 

 on the development of Astroides calycularis (8) that the epitheca of 

 all corals, originally deposited outside the lateral body wall of the 

 embryo, also increases in thickness on the inner side only. 



3. Finally, we find that " diese Koralle bildet einen ganz eigenen 

 Typus, wegcn des giinzlichen Fehlens dcr Inncn-plattc. Die Aussen- 

 platte* tat gut entwickelt . . . Die Homologisirung der Aussen- 



* i.e., E\nth(:c;i. 



