796 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The attempts hitherto made to formulate the succession of the 

 septa in the six-parted corals are at once shown in the annexed dia- 

 gram, which we offer for the sake of comparison. 



Koch. 



1 



4 

 3 

 4 

 2 

 4 

 3 

 4 

 1 



Herr Koch has proceeded by examining, in their proper order, 

 successive slices of single specimens, carefully selected, cleaned, and 

 filled with black sealing-wax. A number of corals belonging to the 

 same species were thus analyzed, one by one, and afterwards compared 

 with each other. Caryophyllia cyaihus was chosen as representing 

 the Imporosa, Dendropliyllia ramea the Perforata. 



The simultaneous appearance of the first six septa contrasts with 

 the very peculiar succession of the primary mesenteries. Herr Koch 

 regards this succession as due to modification. 



In the second section of his present essay Herr Koch maintains 

 that the theca of each corallite among the Anthozoa is formed by 

 secondary coalescence from its septa, and not independently within 

 the body-wall. Four Mediterranean corals, including the two species 

 noted above, appeared to show that the theca really arises in this 

 manner. 



Studies on Gorgoniadse-* — G-. v. Koch associates under the name 

 of Alcyonaria axifera those eight-rayed corals which possess an 

 internal axis but which do not have it, like Corallium, formed of 

 fused spicules, but developed from an axial epithelium ; such forms 

 are Gorgonia, Gorgonella, Muricea, Pruinoa, &c. After describing 

 some new or old species the author passes to an account of the 

 development of G. verrucosa ; the rounded or oval egg is sur- 

 rounded by a hyaline envelope and has a stalk-like process of attach- 

 ment; both these are invested by a cylindrical epithelium derived 

 from the endoderm. The testes are distinguished from the ovaries by 

 their generally paler coloration ; the young spermatozoa are at first 

 rounded, but later on get long delicate tails ; fertilization is always 

 effected within the mother-polyp, and, it is possible, before the egg 

 breaks away from its stalk. In the later stages of segmentation the 

 outer cell-layer becomes converted into a layer of cylindrical epithelium 

 (ectoderm) ; the nuclei of these are smaller than those of the cells 

 within, and the author has been able to confirm his earlier statement 

 that the spicules are developed in the cells of the ectoderm. 



* MT. Zool. Stat. Neapel, iii. (1882) pp. 537-51. 



