1895.] Study of Madreporarian Types of Corals. 



17 



calyces of primitive types. The disappearance of " pinnate inser- 

 tion " as a generic featnre did not necessarily entail the abandon- 

 ment of a tetrameral, more properly said, bilateral, arrangement of 

 the septa. It induced mainly the hastening of septal insertion, the 

 relative position being often retained, even in adult forms * Again, 

 many recent types said to have radial symmetry of septa in adult 

 calyces have well-marked bilateral symmetry in the young in- 

 dividual. 



All the above changes indicate, in the author's opinion, merely 

 various lines of adaptivity, correlative with one great, leading change 

 in the living polyp : — an increase in the number of gonad-bearing 

 mesenteries and in the musculature of the mesenteries, resulting in im- 

 proved powers of self preservation and of reproduction. 



The evolution of recent Madreporarian families from primitive 

 types hinges round the gradual incoming of that main change. The 

 general law of the hastening of the developmental stages in the 

 individual worked with this change, and the pinnate insertion of 

 septal pairs became more and more modified to a cyclical system 

 of insertion. The author points out in favour of this view how the 

 untoward circumstances for coral existence which prevailed in Europe 

 during the Upper Carboniferous, Permian, Triassic, and Liassic 

 ages, may have given a widespread impulse towards the carrying out 

 and confirmation of the main evolutionary change as above stated. 

 The change, however, has been ever since in progress. The author 

 traces its constant working within the family of Astraeidae, its 

 influence on Eupsammidae and Oculinidae, and so on. 



There is therefore, in the author's opinion, no greater fallacy than 

 the idea that some universal change took place amongst Madre- 

 poraria at the end of Palaeozoic time and before the Mid-Triassic era. 

 One and the same line of evolution may be detected making its way 

 in the group of Madreporaria. Precocity in advance was shown by 

 the Palaeozoic Cyathophyllids, hence the high differentiation of 

 Astraeids, Eupsammids, and Fungids as early as Mesozoic ages. On 

 the other hand, the Palaeozoic Zaphrentids and their descendants in 

 Mesozoic times were remarkably backward in advance, and it is 

 among their recent representatives that primitive structures and 

 forms are chiefly upheld. Naturally retrogression and atavism is 

 shown in various degree in all families, in none more so than in 

 the Turbinolids, the family most closely allied with the ancient 

 Zaphrentids. 



The author draws up a new classificatory system of Madreporaria 



* Various observations bearing out this statement have been made by tne 

 author on Mesozoic corals. These are fully described in the author's " Monograph 

 of the Upper Jurassic Stramberg Corals," at present being published in the 

 £ Palaontologische Mittheilungen ' (Koch, Stuttgart). 



VOL- LIX. C 



