116 GEORGE MATTHAI 



distinctly marked off from the solid eiidoderm ' (p. 197). In 

 many of Bourne's figures of the soft parts of the Anthozoa 

 definite cell boundaries are not visible, although such limits 

 have been presupposed in the descriptions. Indeed, in 

 C a r y o p h y 1 1 i a , E u p h y 1 1 i a , ]M a d r e p o r a , and ' several 

 other ' corals Bourne could not find any cell outlines in the 

 calicoblastic layer (7, p. 532), the latter being an irregular 

 multinucleated sheet of protoplasm. When more than one 

 nucleus was present in a mass of protoplasm, it was assumed to 

 be a coenocyte formed by the fusion of uninucleated cells ; 

 for example, in referring to scleroblasts or spicule-forming cells 

 of A 1 c y n a r i a , Bourne remarked that they were ' often 

 coenocytes containing two, three, or more nuclei ' (p. 509), 

 It would appear to be more hkely that the scleroblastic tissue 

 was of the nature of a syncj'-tium in which spicular bodies 

 formed. 



The mucous and granular vacuoles in the outer lamina of the 

 Madreporaria have also been regarded as cells, but nuclei 

 are not definitely related to them, some of them having more 

 than one nucleus while others show none at all. The only 

 cellular elements in the soft parts of the Astraeidae are 

 nematocysts, algal bodies, and the reproductive elements ; 

 these are all characterized by their definite and uniform outline. 

 Nematocysts are secondary formations in the ectoderm for 

 special purposes. Algal bodies are restricted to the endo- 

 derm, but Httle is known of their life-history ; it is doubtful if 

 they are symbiotic organisms, as is generally supposed, since 

 they are found in newly hatched larvae and even in earlier 

 embryonic stages (37, PI. ii, fig. 4). Ova and spermatozoa lie 

 in spaces in the middle lamina (25, figs. 9, 10, and 49). 



The laminae of Astraeid corals are therefore to be regarded 

 as syncytial, and since, as has been seen, there is organic 

 continuity between them, i.e. the ectoderm is everywhere 

 directly continuous with the middle lamina and the latter with 

 the endoderm, and, further, the ectoderm passes into the 

 endoderm by way of the inner linings of the stomodaeum, the 

 tissues form one nucleated continuum which has undergone 



