OF COENOPSAMMIA FROM LIFU. 3G7 



immediately at the top and bottom, end in much convoluted filaments. The primary 

 and secondary mesenteries are attached to the stomodoeum, with which their filaments 

 are continuous, and also reach to the basal wall of the polj'p. AH the mesenteries 

 decrease in breadth with the decrease of the muscular bands, and indeed the tertiary 

 mesenteries are lost with their disappearance (Figs. i. and II.). The filaments of the 

 primary and secondary mesenteries run straight into the polyp below the stomodoeum 

 for 1 — 1"5 mm. before the convolutions commence. The filaments are attached to the 

 mesenteries for their whole length, and are without free portions (acontia) at their 

 lower ends. 



Generative organs. All the polyps, which I have examined by sections — eleven 

 from six colonies — are female, and have no trace of any male generative organs. 

 The ova in each mesentery, in which they are found, are arranged in a row in the 

 structureless membrane between the convoluted mesenterial filament and the great 

 retractor muscle (Fig. Ii.). In the youngest polyps examined (3 mm. across the calice) 

 ova only occurred on the primary mesenteries, but in all the others — eight — had passed 

 into the secondary mesenteries as well. In two large polyps, the one cut into longitudinal 

 and the other into transverse sections, I also found small ova in the structureless 

 membrane of some of the tertiary mesenteries. The ova do not seem to pass into the 

 directive mesenteries as soon as the other primaries, perhaps on account of their being 

 less broad through the elongation of the stomodoeum. 



The ova are presumably formed as in the Hexactiniae from the endoderm, and 

 wander into the structureless membrane (13 and 14). They here wander into the 

 structureless membrane of any mesenteiy, provided that it is of sufficient breadth. I have 

 also found a similar arrangement in Prionastraea ahdita, and it seems very doubtful, 

 whether the order of the mesentery, in which the generative organs are found, is of any 

 importance. 



SECTION III. 



Minute Anatomy. 



Ectoderm. (Figs. 4 and .5.) The external ectoderm, i.e. of the general surface 

 of the colonies outside the tentacles, is very well preserved, and seldom or never 

 detached from the underlying structureless membrane. It is about '03 mm. in thickness, 

 and has a very uniform and much vacuolated appearance. Cell outlines can seldom be 

 distinguished, but it appears to be an epithelium of a columnar facies with a distinct 

 layer of nuclei in the centre. The latter are small, oval, with a few granules and 

 deep staining nuclear membranes. A few smaller, round nuclei, staining homogeneously, 

 are also found, and perhaps belong to sense cells (Fig. 5). Small nematocysts are 

 scattered about, but occur principally opposite to the attachments of the dividing walls 

 of the coenosarcal canals, where the epithelium is rather thicker. They vary up to about 

 •02 mm. in length, and generally have the same structure as the nematocysts of the 

 tentacles. A few, however, are exactly similar, except in size, to the nematocysts found 



on the mesenterial filaments. 



50—2 



