NOTES ON LOPHOPUS CKYSTALLINUS. 
441 
spines are wanting. The disc of the statoblasts in Lophopns 
is of a deep brown colour, seemingly composed of a layer of 
hexagonal cells, a peculiarity in structure also met with in the 
annulus, where, however, the cells are of a somewhat larger 
size and of a different colour ; these cells being filled with air 
impart a fight spongy texture to the statoblasts, and thus act as 
a float, by means of which it is kept at the surface of the water. 
It should here be noticed that these statoblasts are pro- 
duced in the funiculus, along which they may be seen as buds 
in various stages of development, decreasing in size as they 
approach its discal extremity. Under conditions favourable 
for development, the edges of the disc separate, and a young 
polyzoon, in a somewhat advanced stage of growth, emerges 
and floats away in the surrounding water. 
The tentacula alone of the young polyzoon are furnished 
with cilia, and its condition would seem to be passive, with 
the exception of the slight movements produced by their action. 
The little animal is furnished, in all respects, with the same 
apparatus as that met with in the fully developed individual ; 
but it is of a simple and not a compound nature. Soon, how- 
ever, a change takes place, gemmae are developed, and these 
make it assume the compound form of the adult. At present, 
no orifice through which the statoblasts could escape has been 
discovered, although it can hardly be doubted that their 
liberation takes place after the destruction of the soft parts of 
the polyzoon, which giving way afford them free egress. In 
some others of the polyzoa, another kind of statoblast has 
been noticed, but their developmental history is exceedingly 
obscure, and no doubt they are abnormal. 
Thus much for the structure of Lophopus crystallinus. The 
careful observer of its habits and structure will be well repaid 
for his trouble. There is one drawback, however, to com- 
mencing the study of the Polyzoa, for although abundant 
where they do occur, they nevertheless are extremely local. 
The habitats differ with the genera ; some, as Lophopus , de- 
lighting in the clear water of ditches, through which a gentle 
current is running, avoiding exposure to sunlight, while others 
can only be found in stagnant waters. Cristatella , however, 
the only other polyzoon to which a true locomotion has been 
assigned, is to be found in clear lakes and ponds creeping 
along the surface of stones, and the stems of water-plants 
delighting in the full glare of sunlight. 
Description of Plate : — Fig. 1. L. Crystallinus highly magnified. 
a. Calyx ; b. Lophopore ; c. (Esophagus ; d. Intestine ; e. Anus ; /. Pyloric 
cavity of stomach ; g. Cardiac cavity of stomach ; h. Funiculus ; i. Stato- 
blast ; Ic. Ectocyst ; l. Endocyst ; m. Eetractor muscles of polypide. — 
Fig. 2. Lophopus crystallinus, natural size. 
