89 
a gency of life. The Hippothoa, and all the encrusting species 
grow ver y similarly. From one, and sometimes from three 
Points in Hippothoa, a gelatinous transparent looking sub- 
sta >ice is effused of the length, breadth, anil form of the future 
C °H, and in this the lime is soon deposited in the form of a 
Perfect cell. The Tubuliporidie, from the earliest periods in 
' t hich they can be observed have open mouths ; in a very 
e . a r!y state, the polvpe may be said to exist without a tube, 
Slt >ce the calcareous portion forms but a base for the cell, but 
as the polype elongates the tube also increases in length. 
. Whatever opinion may be entertained regarding the poly- 
Pi (| oms of the foregoing orders, those now under consideration 
are generally allowed to have an organic connection with the 
P o| ype ; but the evidence docs not appear to be more con- 
cl Osive here than in the other orders. In the Sea Mats 
' Flustra ) and the kindred genera, the manner in which their 
° r ganic nature can be ascertained, can be seen to the best 
^Vantage, and to these a few observations will be directed. 
f ile encrusting species vary a great deal in shape, which 
l e Pends in a great measure on their different modes of growth. 
Pb e Hippothoa has three points only from which growth 
la kes place: the terminal, which is the most fruitful, and 
J* ne on each side of the cell. At these points a semi-fluid 
j ra nsparent substance is effused, of the form of the cell ; and 
pnee in yonng specimens the cells are connected together 
l,£e loosely strung beads. In old specimens, where each 
has had time to extend its growth from the three points, 
1 greatly resembles an irregular Flustra. In the Flustra 
ubranacea , an exceedingly delicate and guaze-like species, 
IUf e appears to be only one spot for extension, which is not 
? Point, for it extends over all the distal surface of the cells ; 
this gives rise to another which may be called accidental, 
S| °0e it arises from a peculiarity in the cell. The terminal 
longitudinal increase is produced by an effusion of a semi- 
a ’d gelatinous substance, which is called a pulp, and in 
pich the cells are formed. This pulp extends to a certain 
Stance, differing in diflerent specimens, which marks the 
~ le nt of the growth for one time. In a very short time 
a , tlle P ul P is e Hosed, faint white or milky looking streaks 
observed to traverse the pulp in a longitudinal direction 
(j ° fa r as the pulp extends. These lines form the lateral 
l^ondaries of the future cells. At first the lines arc faint, 
‘j fhey sooii become distinct and well defined. I 1 aint 
jjj 1 *y lines are then observed to pass transversely and thus 
ltl VltJ o the space into quadrangular compartments : these are 
6 Ucl ‘ stouter than those first formed. The form of the cell 
t) 1 ' v being completed, no further alteration takes place, but 
e ‘orther condensation of the sides and the formation of the 
