GENERAL AND ANATOMICAL. 
Pol. 5 
surface of the primary animal arises from it. The larvae are not specially 
attracted by light. The discoid organ, ectodermal groove, and gland are 
withdrawn into the interior ; as also the flagella and cilia. The view of 
Barrois that the development is not a metagenesis, but a true metamor- 
phosis, is supported; Yigelius (2). 
The larvae of the Cyclostomata are the simplest among the marine 
Polyzoa. Their whole surface is ciliated ; there is a sucker at one pole, 
at the other the mantle cavity. The entodermal cavity disappears before 
the extrusion of the larva ; there are no provisional organs. The meta- 
morphosis begins with the protrusion of the basal wall of the primary 
zooecium and with the flexion of the mantle. The basal wall widens and 
forms a kind of stolo prolifer (“ lame germinale,” d’Orb.). The ectoderm 
of the polypide is formed of a plate split off from the ectodermal 
cells. The process recalls that which occurs in the Vesicularice. The 
Incrustata and Stolonifera unite the Cyclostomata and Ctenostomata ; 
Ostrooumoff'(2). 
In the larvae of freshwater Polyzoa the posterior ectodermal cells are 
much higher than those of the rest of the body, being possibly homo- 
logous with the sucker of marine Ectoprocta. The metamorphosis of 
Alcyonella is divisible into two stages : — (1) The mantle bends over on 
the basal side ; this is common to all Ectoprocta. (2) In the freshwater 
forms only the basal side and edges of the mantle are invaginated, so that 
the ascending portion of the mantle-cavity forms a canal, the walls of 
which soon fuse, and from which the body-wall of the primary zooecium 
is alone developed ; Ostrooumoff (3). 
The post-larval chauges in Pedicellina consist in a remarkable 
metamorphosis, and the first bud is formed after the primary individual 
is adult. The metamorphosis is perhaps an abbreviation of some 
more archaic process. The growing point of a stolon seems to consist 
only of ectoderm and cuticle, enclosing structureless jelly and con- 
nective tissue corpuscles : the brown bodies are regarded as degenerate 
polypides ; the degenerative process is too slight to give rise to them 
in Pedicellina ; Harmer. 
As the result of studies of the development of Lepralia , Bugula, 
Serialaria , and Pedicellina , full details regarding which are given, the 
following conclusions are formulated : — Two chief typical modes of 
metamorphosis may be distinguished — that of Phoronis and that of Pedi- 
cellina. The former is characterized by the predominance of the ven- 
tral surface, which forms the bulk of the body, and the reduction of 
the dorsal surface to a terminal region; the second by the predomi- 
nance of the aboral surface (cephalic aspect of the trochosphere), which 
stretches entirely above the oral surface in order to form the whole 
oxtornal surfaco of tho adult, whilst tlio wholo somatic face is crowded 
into the interior. The Polyzoa , as a whole, are placed in the second cate- 
gory, as opposed to Phoronis , and perhaps Bhahdopleura , in the first ; 
both are derived from the trochosphere ; Barrois. 
The Phylactolcemata may have been derived from such forms as 
Arachnidium and Victorella among the Gymnolcemata. The Paludicelloe 
with winter buds were probably the first to develop ; these “ hiber- 
