14 SPONGES hh Pyey 
the truc position of the incurrent openings, and their number, but conside: ably 
enlarged. 
On the other hand, the excurrent openings are not numerous And are 
seldom or never found near the mouth of the great central tube. ‘Thus it will 
be seen that, from necessity, one system of cells, which. hasno direct. coma ui; 
cation with any excurrent opening, must empty its ccntents - into another -sys- 
tem that does, and this is frequently the case. ‘There is another method, how- 
ever, which I have found near the termination of a cylinder, that was cight 
inches long. Here one excurrent tube opened into a long, tubular cell, that, 
extending upward, received the contents of no less than six cell ‘systems, each 
successive one growing shorter, as the sponge grew thinner toward its termina- 
ation. All of these cell systems opened in a line on the inside, but became 
diffused somewhat externally to meet their respective incurrent tubes. This 
should be kept in mind in consultiug the diagram at Fig. ¥, where this system 
is given at A. 
L shows aside view of the elongated chamber, lying just within the 
skin of the central tube, with the six cell systems opening into it, and below it 
is a top view of the same, allof the circular dots being the position of the in- 
current communication with the cell, excepting c, which is the excurrent open- 
ing in both top and side views. Another method of the concentration of the 
incurrent tubes may be seenat Fig. 2, A, where the incurrent tubes, a, a, ‘a. 
open into a common water system, 1, which is quite wide. The actual number 
and position of the excurrent openings in one half of the central tube of a small 
size sponge may be seen at Fig. g, near the bottom of the tube, O. ‘There were 
eight of them (represented in the figure by the dots ) in this half, and about 
the same number in the other half, and none at all near the mouth of the 
tube, and this is quite usual in this species of Verongia. 
