12 Miss M. M. Ogilvie. Microscopic and Systematic [Nov. 21, 



reous secretion and the less complete calcification of the calicoblasts 

 present at the doubled upper edges of septal invaginations. In fossil 

 material, secondary changes render this central part of the septum 

 more or less conspicuous on account of the breaking down of organic 

 products, or sometimes the complete replacement by infiltrated salts. 

 The author strongly contends that there is no basis for the assump- 

 tion of a " primary septum" in the middle plane of a septum in the 

 sense at present accepted by most palaeontologists. On the contrary, 

 the author's sections show that the fibro-crystalline structure of the 

 septum is the same throughout its whole thickness, essentially that of a 

 double system of thin calcareous lamellce, either smooth or fluted, and 

 corresponding to a deposit from opposite flaps of an invagination. 



The author's investigations afford many new microscopic facts of 

 structure testifying that the growth in height of the polyp is accom- 

 plished at certain growth-periods, between which pauses ensue. 

 During each growth-period a varying number of the calcareous 

 lamellae, u growth lamellae," are laid down, and these always appear 

 in intimate union with one another. Again, regular curves or lines 

 of growth are evident on the septal surfaces, marking the intervals 

 between successive growth-periods. The space between two growth- 

 curves or lines on the septal surface represents the part of the septum 

 built up in one growth-period, and it has been called by the author a 

 septal growth-segment. An important observation is that the extra 

 length added to a single trabecula in one growth-period is invariably 

 one trabecidar part ; this length varies in the trabeculae of one and the 

 same septum, being greatest at the exsert portions near the wall. 



Granulations mark the surfaces of trabecular parts. Edwards and 

 Haime applied the term " synapticula " to the interseptal bars in 

 Fungia and its allies, and described the synapticula as formed by 

 coalescence of granulations from opposite surfaces of neighbouring 

 septa. The author demonstrates that in Fungia the granulations 

 seldom meet across interseptal loculi. But a continuous calcareous- 

 deposit is formed in a special invagination of the interseptal parts of 

 the aboral body-wall. Together with a number of observations on 

 other synapticulate types, this has led the author to accept a distinc- 

 tion made by Pratz, and hitherto discredited in the literature. 

 Pratz proved that the fossil Fungid subfamily of Thamnastraeinae 

 had synapticulae formed by coalescence of granulations, and these he 

 called "^seMtZosynapticulae." The name of " true synapticulae " he 

 limited to such as were formed around new centres of deposit out of 

 the septal plane ; these he found in Siderastraea, but did not farther 

 examine typical genera belonging to the families Funginae and Lop- 

 hoserinae. The author's results are that pseudosynapticulai occur not 

 only in Thamnastraeinae, but also in the Funginae, Lophoserinae, and 

 occasionally in Astraeidae and Eupsammidae. While true synapticula 



