62 
HE VIEWS. 
Three modes of development occur among the Polyzoa, viz., first, 
true reproduction by ova; secondly, by gemmae j and thirdly, by bodies 
of a peculiar nature termed statoblasts, which, however, may be re¬ 
garded as “ gemmae in which the developmental activity remains for 
a time latent.” The structure and mode of growth of these statoblasts 
are often exceedingly curious. In some Polyzoa the multiplication of the 
compound structure takes place by a process of self-division. This mode 
of increase may be referred, however, to the second of the above methods, 
for, as Dr. Allman truly observes, there is no real difference between gem¬ 
mation and fission. 
The classification of the Polyzoa proposed by Dr. Allman will be 
best understood by an inspection of the following Table:— 
Class— POLYZOA. 
ORDERS. 
SUB-ORDERS. 
Lophophore bilateral; 
mouth with an epis- 
tome. 
Phylactoloemata. 
Arms of lophophore free or 
obsolete. 
Arms of lophophore united at 
^the extremities. 
Polypide only partially retrac¬ 
tile. 
Lophophoea (fresh water). 
| Pedicellinea (marine). 
> Urnatellea (fresh water). 
Polypide completely retrac¬ 
tile ; evagination of tentacular 
sheath imperfect. 
Paludicellea (fresh water). 
Lophophore orbicular, 
or nearly so; no < 
epistome. 
Gymnoloemata. 
Polypide completely retrac¬ 
tile ; evagination perfect; orifice 
of cell destitute of movable ap¬ 
pendage. 
Polypide completely retrac¬ 
tile; evagination perfect; a cir¬ 
cle of setae attached to the inver¬ 
tible portion, and acting as an 
operculum in the retracted state. 
Cyclostomata (marine). 
> Ctenostomata (marine). 
Polypide completely retrac- ) 
tile; evagination perfect; orifice >Cheilostomata (marine). 
v of the cell with a movable lip. J 
The fresh-water species are referred to eight genera. Of these, six 
are included under the sub-order Lophophoea, which is divided into two 
families : Cristatellidse, which contains but one genus, Cristatella; and 
Plumatellidee, which contains five, viz., Pectinatella, Lophopus, Alcyo- 
nella, Plumatella, and Predericella. The sub-orders, Urnatellea and 
Paludicellea, include each but one family and one genus, named respec¬ 
tively Urnatella and Paludicella. 
All the.known fresh-water species, both Pritish and foreign, are de¬ 
scribed in Dr. Allman’s monograph. Of the twenty-one species mentioned, 
seventeen are found in the British Isles. Many of these are now de- 
