10 Spong. 
XYlI. SPONQIiE. 
cells. It ia thin on the upper side, but attains a considerable thickness on 
the lower face of the Sponge, where it surrounds the basal lacunes and 
forms the stolons by means of which the Sponge is fixed to the ground. 
f. Interstitial Layer (61). 
Topsent (61) states that in the Carnosa this layer is sometimes 
( Chondrosia ) very voluminous, and quite encloses the ciliated chambers, 
whilst in other forms ( Placina ) it is only slightly developed. 
q. Sexual Cells, Propagation, and Development 
(14, 40, 49, 61). 
Delage (14) says that the statoblasts of Spongillidce are apparently 
nothing but indifferent portions of the body tissue, separated from the 
rest and surrounded by a capsule. 
Lendenfeld (40) upholds the correctness of Sollas’s figures of blastulae 
of Oscarella against Heider. 
Montgomery (49) quotes two cases of protandric hermaphroditism in 
Sponges. 
Topsent ( 61) vainly sought for sexual cells in Chondrosia and Dercitus 
in the winter months. 
h. Physiology (5, 29, 40, 43, 61). 
Bidder (5) has made feeding experiments on Sponges. His results 
give, in every point, fresh testimony to the five conclusions drawn from 
his own experiments previously by the Recorder. Only in one point of 
less importance, not contained in these five theses, Bidder has come to a 
different conclusion. He thinks that the presence of carmine- and starch- 
grains in the surrounding water does not induce the Sponge to contract 
its pores. He has been just as unable, as was previously the Recorder, 
to discover anything in support of the views entertained by Sollas and 
Mastermau concerning the sinking of collar-cells, when full of nutriment, 
into the interstitial layer, and there being transformed into amoeboid 
cells. Migration of collar-cells does seem to occur occasionally, but rarely, 
and then only under exceptionally unhealthy conditions. In certain 
pathological circumstances, probably connected with suffocation, the 
collar-cells elongate very greatly, diminishing in the diameter of the upper 
part, or collum. In certain other pathological conditions the collar is 
lost, though apparently it can be regenerated. 
Lendenfeld (40) gives the reason whyHeider’s statements concerning 
the absorption of carmine by the collar-cells were not separately quoted 
by him. 
Topsent (61) states that Dercitus plicatus is white, but contaius 
in the interior yellow cells which sometimes become violet. He has 
also observed this change of colour taking place after the Sponge was 
immersed in alcohol. 
