32 On the PrototJieca of the Madreporaria. 



The curved line a represents the secretion of the basal skin 

 after it has been dragged (?) out of the prototheca by the 

 growth of the walls in height; b represents the secretion 

 formed by the shin after it has become detached from a. 



Fig. 2. The same regarded hypotketicfilly as three separate cups, the 

 lowest thick-walled cup being the prototheca (sens, strict.) ; in 

 it cup a a ais inserted, and cup bbb in a a a. 



Fig. 3. A diagram to explain the morphology of Montlivaltia. The 

 early cups rapidly expand and eventually become a series of 

 saucers, e e . ., supported above one another by the septal folds 

 which run continuously upwards. On the right half of the 

 figure the upper part is in section, showing the tabulate floor 

 and the irregularly bent-up rim. On the left half these rims 

 are shown from the outside as irregular bands of epitheca 

 running round the coral. 



Fig. 4. An early stage like that of fig. 1, but, having fallen over and 

 resecreted itself at «, it bends upwards again. The bagging 

 of the detached basal skins will take the shapes shown, and 

 the fossula in the bases of the cups will be on the convex or 

 dorsal side of the curved skeleton. 



Fig. 5. A diagram to show how, if the prototheca proper was wide- 

 mouthed when it fell over, the fossula will come over to the 

 ventral or concave side. <t is again the spot where the coral 

 secretes a new attachment. 



Fig. 6. The diagrammatic representation of the arrangement of the 

 septa in the so-called Tetracorallia. It receives a simple 

 explanation as due to the necessary rearrangement of the septa 

 in a coral which fell over and was bending up again. See text, 

 p. 11. 



Fig. 7. Diagram to illustrate the method of budding of a prone proto- 

 theca and the subsequent bending upwards of parent and buds 

 which might give rise to such a form as Hall/sites. 



Fig. #. Two figures of radicle-formation, after Lacaze-Duthiers. 



Fig. 9. Diagram to illustrate the one-sided bend-over of the prototheca 

 such as it is suggested would give rise to the Zaphrentis 

 gigantea of Milne-Edwards and Ilaime. See text, p. 14. 



Fig. 10. Diagram to explain the early flattening out of the prototheca in 

 the Perforata. The rim of the cup creeps outwards all 

 round, generally with successive slight bendings up and then 

 down again. 



Fig. 11. Diagram of the early stages in Palceocyclus. The prototheca 

 proper seems to have fallen over and then suddenly to have 

 widened out, the repetition of this is still more widened out, 

 and so on. AVhat appears to have been a wrinkled basal 

 epitheca is not a continuous growth like that in fig. 10, but a 

 repetition of so many separate protothecal rims. 



Fig. 12. Diagram of the early stage of Cgclolites. The prototheca is 

 nearly flattened out, but it is still repeated continually, only 

 instead of the secretions of the successively detached skins 

 forming continuous tabulae, they are broken up into vesicular 

 dissepiments. Here also what appears to be the wrinkled 

 epithecal floor is in reality a concentric series of separate rims. 



Figs. 13 a-g. Various forms assumed by the protothecee in Palaeozoic 

 corals, all in the direction of becoming flattened out. The 

 developmental transitional stages between the deep proto- 

 theca and these adult forms have & t ill in many cases to be 

 worked out. 



