280 Brown — Developmental Stages in Strejptelasma rectum. 



cardinal quadrant. In fig. 7 two secondary septa have 

 appeared in each cardinal quadrant, and in fig. 8 four are 

 present in each counter quadrant. In tig. 9 there are three in 

 each cardinal quadrant and five in each counter quadrant. 

 Fig. 10 has four secondary septa in each cardinal quadrant 

 and six in each counter quadrant. Attention is called to the 

 grouping of the septa in this and the preceding figures. Each 

 successive septum to appear in each quadrant respectively is 

 attached by its inner border to the side of the previous sep- 

 tum, giving in this stage an arrangement of the septa similar 



to the adult condition in the genus Hadrophyllum.* Fig. 11 

 has the same number of secondary septa but they are all more 

 fully developed, and in addition three more pairs of tertiary 

 septa (exosepta) have been added in the counter quadrants and 

 two pairs have appeared in the cardinal quadrants. In fig. 12 

 a seventh pair of secondary septa have appeared in the counter 

 quadrants, making the total number of secondary septa present 

 in the adult corallite. Two more pairs of tertiary septa are 

 added in the counter quadrants and three more in the cardinal 

 quadrants. Fig. 13 is a section from near the base of the 

 calyx. All the primary and secondary septa project freely 

 into the cup. The cardinal septum is hardly as large as the 

 others. The alar septa and all the secondary septa are about 

 equally developed and each has a tertiary septum abutting 

 against it. The counter septum is a little stronger developed 

 and longer than any of the others and has a tertiary septum on 

 either side. 



*See, also, J. E. Duerden, Biological Bulletin, vol. ix, No. 1, pp. 35, 36, 

 June, 1905. This also corresponds to adult in S. profundum. 



