310 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 



scarce in a. I observed a large number of these small micramphidiscs in situ 

 in the gastral membrane of specimen b, where they lie in large part paratangen- 

 tially with their shafts parallel to the surface; and I found a great many also 

 in the centrifuge spicule-preparations of specimen b, both in this membrane 

 and in the choanosome. One- to six-rayed acanthophores with terminally 

 or, much more rarely, entirely spined rays are abundant in both specimens in 

 the vicinity of the point of origin of the stalk. In specimen a these spicules 

 are on the whole stouter than in specimen b. The skeleton of the stalk extends 

 through the body of the sponge up to the gastral cone. Its upper, imbedded 

 part consists of centrostyle amphioxes and the upper end-parts of the large 

 spicules forming the free part. The latter, provided it really belongs to the 

 sponge, is in specimen b (Plate 82, fig. 1) composed of five stout and about a 

 dozen more slender spicules twisted spirally together. The free part of the 

 stalk of specimen b is composed of about a dozen stout and a small number of 

 slender spicules. 



The symbiotic zoantharian polyps. To the proximal end-part of the stalk 

 of specimen a is attached a tubular Palythoa colony, enclosing the stalk like 

 a tight-fitting mantle for a distance of 17 mm. The individual polyps arising 

 from this tubular colony are about 3 mm. high and 4 mm. broad. Polyps 

 and coenenchym are provided with a stout skeleton composed entirely of acan- 

 thophores of the sponge, to the stalk of which the colony is attached (Plate 84, 

 fig. 1). In the polyps longer and more slender spicules lying radially in the 

 radii of the septa occupy the oral plate, and perhaps also the upper parts of 

 the septa. In the superficial parts of the lateral walls of the polyps and the 

 coenenchym shorter, stouter, and on the whole more spiny spicules, lying close 

 together, form a dense cortex. Still shorter, stouter, and more spiny spicules 

 are found near the axis around the mouth and in the wall of the stomatodeal 

 funnel. 



On the stalk which probably belonged to specimen b no polyps were 

 observed. Its proximal end-part is, however, enveloped by a thin mantle 

 (Plate 82, fig. 1) brown in colour, chitinous in nature, and entirely destitute of 

 spicules; this mantle may be the basal part of the coenenchym of a zoantha- 

 rian polyp-colony. In the body of specimen a no symbiotic polyps were 

 observed; the dermal region of the body of b on the other hand contains a 

 large number of such polyps (Plate 82, fig. 1; Plate 83, fig. 60a). These polyps 

 (Plate 84, fig. 14) are Zoanthidae. They contain no spicules at all and are, 

 in their present contracted state, nearly spherical, and 1.3-1.8 mm. in diameter. 



