REPORT ON CORALS — EXPLANATION OF PLATES. 221 



E. Ectoderm here containing very few nematocysts but numerous nuclei. 

 T, T. Tentacles in section. 

 Fig. 2. Section transverse to the longitudinal axis of a large dactylozooid of Spota- 

 clopora dichotoma. 



B. Body cavity of the zooid. 



L. Endoderm consisting of a double layer of large transparent nucleated 



cells with smaller cells on its inner aspect. 

 M. Muscular layer and basement membrane showing a series of stout 



isolated fibres. 

 E. Ectoderm. This forms a thick layer which contains numerous nuclei 

 and developing nematocysts, and at its outer surface is protected 

 by a continuous layer, one cell deep, of nematocysts of the 

 smaller form. 

 Fig. 3. Section parallel to the surface of the soft tissues of Spovadopora dichotoma 

 taken at a very slight depth just beneath the superficial layer of the 

 ectoderm. The soft structures about the mouths of the sacs of a 

 gastrozooid and a contiguous dactylozooid are shown, and the radiate 

 arrangement of the ccenosarcal tubes around the sac openings. 

 G Z. Lumen of the upper part of the sac of a gastrozooid. 

 E M. Wall of the sac containing radially disposed fusiform muscular 

 elements which are prolonged outwards on to the radial offsets of 

 the ccenosarc. The wall of the sac is lined internally by small 

 rounded cells. 



B, B. Badially disposed, offsets of the ccenosarcal meshwork • which pass 



inwards to join the outer surface of the sac all round. 

 A, A. Slips of fine transparent membrane containing nuclei attached to 



the radial offsets. 

 X, X. Inter-radial spaces. 

 D Z. Lumen of the sac of a dactylozooid with somewhat similar 



arrangement to that in the case of the gastrozooid. 

 N, N. Nematophores. Closely packed batteries of the larger form of 



nematocysts, which are here seen in transverse section. 

 Fig. 4. Tentacle of a gastrozooid of Spovadopora dichotoma, from a sketch made of 

 the animal in the fresh condition. 



K. Elongate knob-like tip of the tentacle thickly beset with nematocysts 



of the smaller form. 

 E. Ectoderm. 

 Tr. " Apparent septa." 



C. Axial cavity of the tentacle. 



