538 EDITH M. PRATT. 



Fig. 14. Longitudinal section through four siphonozooids of the same species (Si^, Si.,, Si^, 8%), 

 showing ciliated vessels connecting the coelenteric cavities. The section passes through 

 the siphonoglyph of the first siphonozooid. Only the left half of the fourth siphonozooid 

 is indicated. 



Fig. 15. Sclerophytum capitate. Clubbed spicule. These are very abundant near the surface of 

 the colony, x 219. 



Fig. 16. Different forms of the tuberculate spicules to be found in a single colony of the same 

 species, x 20. (Regular spindles, similar to those of other species, are also numerous, 

 but they are not figured.) 



Fig. 17. Surface view of a portion of the capitulum of the same species, showing arrangement of 

 siphonozooids between two autozooids. x 45. One of the autozooids is partially contracted, 

 the other is fairly well expanded. The tentacles have a double row of small pinnules 

 down each side. 



Fig. 18. Sclerophytwn densum. Young colony, showing formation of primary lobes from the margin 

 of the capitulum. The colony has not yet lost its mushroom-like form. The surface of 

 the capitulum is slightly concave. The siphonozooids are very minute and are not in- 

 dicated in the drawing, x 1^. 



Fig. 19. Sclerophytum capitate (sp. nov.). Drawing of a fairly thick free-hand section through a 

 lobe of the capitulum of the same species, x 65 (Cam. Lucida). The drawing shows 

 the rudimentary siphonozooids which terminate posteriorly in the transverse vessels of 

 the superficial canal system. The vessels of this system communicate with those of the 

 internal canal system, and directly or otherwise with the coelenteric cavity of the 

 neighbouring autozooid. 



Fig. 20. Scterophyluni densum. a, h, c, d, e. Different forms of tuberculated spicules characteristic 

 of the genus, x 10. /. A forked spicule with irregular tubercles. g, ]i. Two tubercles 

 seen laterally, x 300 (Cam. Luc). 



Fig. 21. Longitudinal section through a single degenerate siphonozooid of same species, x 730. 

 The section passes through the mouth aperture of the siphonozooid. The stomodaeum 

 is extremely short in this specimen. A deeply staining layer of dense mesogloea sur- 

 rounds the siphonozooid internally. Tlie siphonozooid passes posteriorly (on the left) into 

 a superficial transverse vessel. The endoderm lining the coelenteric cavity is distorted 

 by the presence of numerous zoochlorellae. An aggregation of endodermal cells near 

 the stomodaeum is probably a degenerate mesentery. 



Fig. 22. A partially retracted autozooid of same species. The drawing was made from a fairly 

 thick freehand longitudinal section stained with borax carmine. The figure shows the 

 intimate connection between the coelenteric cavity of the autozooid and the lumen of 

 the canals, and also with the coelenteric cavity of the degenerate siphonozooids. The 

 long stomodaeum is shown (dotted shading). Tlie ventral and lateral mesenterial fila- 

 ments are very short. The dorsal mesenterial filament is long, ciliated, and grooved. 



Fig. 23. Sclerophytian hirtum. Drawing of a colony to show lobation of capitulum. x IJ. Most 

 of the autozooids are partially expanded. 



Fig. 24. Spicules of same species, a, b, c, d, tuberculate spicules ; e, f, clubs. 



