128 
The next suborder is the Ctenostomata which is dis- 
tinguished by the cell orifice being surrounded by a fringe 
of bristles. These are horny or fleshy, and none are calca- 
reous, and have a soft stalk with zooecia springing out from 
the side. 
The Endoprocta (Pedicellina, &c.) consist of some half 
dozen species on the border land, and need not be further 
discussed in remarks of so general a character. 
The form of the Bryozoa is very various, but all are fixed, 
and this, as we have seen, was so much associated with 
vegetable life that it was one of the reasons which led to 
the strange conceptions alluded to. 
The marine forms live at various depths, occurring pro- 
bably in greatest abundance in from 20—100 fathoms, but 
there are also many species living just below low water; 
and here, as with other marine animals, we can, from the 
species, judge of the depth. In depths where the currents 
are slight and which we may consider as below the Lamin- 
arian the firm forms as Eschara, Idmonea, Retepora, &c., 
abound, whereas in the zone, where they would be broken by 
the moving waters none, except incrusting forms, are rigid for 
any considerable extent, but some have chitinous joints at 
shorter or longer intervals as in Crisia, Cellaria, Salicornaria, 
&c., some have but very little calcareous matter so that they 
are flexible like most Flustra and the Ctenostomata, and even 
in Flustra membranacea the thin calcareous portion has been 
shown by Nitsche to be in discontinuous plates, thus giving a 
a large degree of flexibility to this semi-calcareous species. 
Although the rigid forms are not found in the lesser depths 
many of those of great flexibibility as species of Crisia Sali- 
cornaria, &c., &c., are found in the deeper waters. The 
Challenger found Bryozoa at all depths, and doubtless this 
expedition will add very much to our knowledge of their 
range about which but little is yet known. 
In many the branches anastomose, thus forming a reticu- 
