22 R. KIRKPATRICK. 
there is the extremely fine square-meshed reticulum formed by the tangential rays 
of the autodermal pentactins. Beneath this are subdermal spaces separated by the 
proximal rays of the pentactins from the hypodermal network with its much larger 
triangular or trapezoidal meshes. The strands of the hypodermal network are formed 
of straight tangentially arranged bundles of rather thick diactins. The gastral region, 
on the other hand, is without subgastral network and spaces, and the bundles of diactin 
principalia are not distinguishable from those of the rest of the parenchyma. 
Canal-System and Soft Tissues.—The main exhalant canals run vertically 
upwards from base to summit, receiving lateral branches in their course. A section 
shows circles of the flagellated chambers opening into the finer canals. The subdermal 
trabecular network, and the lining of many of the exhalant canals, are crowded with 
masses of knollen-thesocytes, each thesocyte being about 8-10u in diameter. In 
unstained balsam preparations these masses of thesocytes are clearly distinguished 
by their dark yellow colour ; further, they take a deeper stain with borax carmine 
than do the rest of the sponge tissues. 
The skeleton is formed mainly of bundles of diactins and of separate large 
hexactins, pentactins, stauractins, and tauactins. 
Spicules.—The principalia are diactins which vary considerably in length and 
thickness, the average kind being about 7560 x 22y, tapering to fine points and 
spined at the extremities. The spicules, which, in specimen A, are regarded as possible 
marginalia, are in the form of two or three long curved diactins about 5 em. in length. 
They have become misplaced, and possibly may not belong to the sponge. The delicate 
marginalia in specimen C project about 6 mm., and are about 13 mm. in length. 
The little tufts of diactin basalia are about 2°5 cm. in length. 
The large regular hexactins (V. 2a) have rays 800 x 60y, slightly spined at the 
ends ; large pentactins, stauractins, and tauactins (V. 2b, c, d) also are present. 
The autodermalia (V. 2e) are pentactins with rays 172 x 24°5y, closely spined. 
Young pentactins with fine, smooth, sharp rays occur both in the dermal and gastral 
layers. 
The autogastralia are mostly pentactins similar to the autodermalia ; a few small 
regular hexactins also occur, especially in specimen C. Plate V., figs. 2f-2f', shows 
several modified hexactins and a pentactin from the region round the single exhalant 
orifice in specimen C. 
The intermedia. Oxyhexasters. Holoxyhexasters (V. 2g), 197, with bifurcate 
primary rays, short or almost absent, are pot uncommon; a kind (V. 2g"), 86, in 
which each primary ray ends in a disk, whence five to six sharp-pointed secondary rays 
diverge, occurs less frequently. 
Hemioxyhexasters (V. 29°), about 180m, are abundant; and monoxyhexasters 
(Y. 2g°*), also about 180 in diameter, occur, but rarely; fig. 29? shows a hemi- 
oxyhexaster in which one of the secondary rays has a trifid termination. (The small 
“2” of 29° has been omitted in the plate.) 
