282 I. IJTMA : HEXACTINELLIDA. I. 



Sometimes but a narrow bridge-like space intervenes between two 

 adjacent oscula ; more frequently are they situated more than 

 100 mm. and at times even 200 mm. apart on the same side of 

 the stem. Their total number is therefore never very great. In 

 a large specimen with a height of 855 mm., I have counted iu 

 all not more than 25 oscula on the stem. The u^Dpermost osculum 

 may lie within a distance of 10 mm. or so from the apical end. 

 Inferiorly, an osculum may occur right at the stem-base and, as 

 before mentioned, even on the basal disc. There apparently 

 exists no definite relation between the distribution or size of 

 oscula and the develo2:»ment of lateral branches. 



Seen with the naked eye or under a lens, the surface of the 

 lower stem-end shows the same structural character as the basal 

 disc, — that is to say, a densely interwoven texture of fine spicules 

 intersecting in all directions. On these parts, a loose superficial 

 tissue is usually entirely wanting. Such a tissue generally begins 

 to exist on the stem a few centimeters from the base and covers 

 the rest of the sponge parts in a thin, but by no means uni- 

 formly distributed, layer. This tissue, together with warty 

 protuberances on the stem and the branches, gives to the sponge 

 an appearance fittingly described by Mooee to be, ' as if the 

 specimen had been dipped into a thick soap lather, which had 

 been allowed to dry on its surface.' 



Through that covering layer can be plainly observed the 

 outer spicular bundles of the parenchyma, traversing the stem on 

 the whole in a longitudinal direction. They are of varying 

 thickness and closely set, frequentl}^ uniting and again separating 

 in their course or sometimes intersecting one another at low 

 ansfles. 



