466 Mr Gardiner, Notes on Variation, 



fresh acini an oval mass is formed. When the calicle is about 

 13 mm. long, fresh testicular elements cease to be added to the 

 primary mesenteries — those which reach the stomodoeum — and 

 further change takes place merely in the enlargement of the 

 acini with increase of spermatozoa, their shape becoming poly- 

 gonal or quite irregular. Meantime the smaller mesenteries 

 gradually develop their testes. 



When the length is 15 — 17 mm., all the mesenteries have 

 testes, but only those on the larger mesenteries are as yet 

 functional. The spermatozoa appear to escape by temporary 

 ducts, all in each single acinus being shed together. The corallum, 

 in the type variety, has at this period usually 20 septa fusing by 

 trabeculae in the axial fossa. In 51 specimens out of 65 of this 

 size the number of these larger septa is 20, constituting a very 

 determinate stage. The appearance is so regular indeed that 

 Semper considered that he had here a true case of 5-rayed sym- 

 metry, whereas the development shows clearly that the true 

 symmetry is hexacoralline in accordance with Milne-Edwards' 

 law. The corallum in the Cape specimens, when of this size, 

 has 5 lines of growth which correspond probably to annual 

 periods, and it is interesting to observe that the specimens figured 

 by Semper exhibit the same number. 



In still larger specimens of about 20 mm. in length ova com- 

 mence to appear in the generative masses on their inner sides — 

 i.e. towards their free edges — which are of course terminated by 

 the mesenterial filaments. Each gonad now consists on its outer 

 side of a series of closely set irregular sperm acini with definite 

 open spaces in their centres, hence more or less ripe. On the 

 inner side the acini are more rounded and less crowded, but some 

 trace at least of the central space is visible. The ova, generally 

 2 to 4, appear on the inner edge near the upper end of the mass, 

 and are at first quite minute. No further sperm acini are now 

 added. As more and more of the older acini extrude their con- 

 tents, the newer ones and the ova fill their space. The ova grow 

 enormously, with the final result that the mass becomes entirely 

 female, consisting of usually 2 or 3 large ova, flattened on their 

 sides against one another and occupying the whole area of the 

 former testis. 



Together with the above changes the corallum becomes more 

 rounded and less pointed at the ends of the axial fossa. The 

 epitheca is considerably thickened by fresh deposition of corallum 

 within the calicle, and indeed there seems to be everywhere 

 a renewal as it were of the activity of the calicoblast layer. The 

 wings of the calicle are filled in with corallum, and may be much 

 worn down outside, perhaps leaving hollow spines, filled in life 

 with extensions of the polyp. This change, though, is due to 



