ANATOMY. 
Spong. 5 
or lateral finger-like evaginations, the calyx-wall may become compli- 
cated, as in Aphrocallistes bocagii , in which the gastral cavity is divided 
into several chambers (one lying behind the other) by net-like dia- 
phragms. 
If in a stalked originally calyciform example the outer edge turn 
down after complete opening out of the cup, a mushroom form origi- 
nates. Thus the original gastral cavity disappears, and the original gastral 
surface becomes the upper and outer surface of the Sponge. This process 
may be carried still further, the oscular edge continuing to turn down 
till it produces a cylindrical or nearly hemispherical body, the outer 
surface of which is gastral, and continuous with that which lines the 
cavity of the tubular stalk. 
In many Dictyonina the sac-like form elongates, without any consider- 
able thickening of the wall, to form thin walled tubes, which then become 
branched, often dichotomously, and subsequently the neighbouring 
branches anastomose and so form a tubular plexus, from which numerous 
terminal branches project, each with a single oscular opening. 
A funnel-shaped form sometimes gives rise to lateral tubes which 
branch and anastomose (ex. gr. Periphragella): or a system of anastomosing 
tubes, which open to the exterior, may euclose a central cavity, with 
which they may or may not be in communication ; this cavity is a 
Pseudogaster. In such forms there sometimes occurs, covering the 
whole exterior, a special capsule or investing layer, which forms a sieve- 
net over the incurrent openings, and a sieve-plate over the oscules (ex. gr. 
Sempcrclla). 
Genital products occur in tho connective tissuo of tho sub-dermal 
cavity; the sperm-balls resemble those of other Siliceous Sponges, such as 
Reniera and Spongilla. The ova are at first scarcely, or not at all, to be 
distinguished from connective tissue cells, but are recognized later by 
their considerable increase in size and by the appearance of numerous 
yelk-granules, as well as by the enlargement of the nucleus, which in some 
cases, instead of lying in the interior, is situated in a depression of the 
surface of the ovum. Segmentation stages were not seen. 
In some species multiplication by budding occurs. This may be well 
studied in Polyophus philippinensis. Conical processes bearing a bundle 
of gently diverging spicules project from the lateral surface, they 
increase in size and become teat-shaped, the base becomes constricted, 
the outer part pear-shaped ; the pear-shaped part in particular enlarges,* 
a round opening appears at the distal pole, while from the lateral 
surface conical elevations, bearing projecting bundles, and irregu- 
larly distributed, arise, and thus cause the bud to resemble the parent. 
The connecting stalk becomes longer and thinner, and finally can no 
longer support the bud, which is set free. Should the buds remain in 
union, there would result a branched stock with branched stem, such as 
0. Schmidt has described in Sympagella nux. Young buds are particularly 
valuable in affording an insight into the general structure of the grown- 
up Sponge ; longitudinal sections show with particular clearness the 
relations of the folded chamber-layer to the canal system. 
Lampe (18) describes the anatomy of a new species of Tetilla ( T . 
