“dies are very interesting and are produced by minute 
. 'bratile cilia which cover their surfaces and are generally 
r apid motion. By means of these cilia the gemmules re- 
°'ye on their own axes from spot to spot, sometimes with a 
j" a pid gliding motion, at others by sudden springs; then 
l °Pping, and again bounding away to other spots, changing 
forms from round to oval or irregular; but having 
•,?^ n d a situation on which to fix, they generally become oval, 
i be time during which they remain tree varies from a few 
j?' lr s to two days, depending on the collateral circumstances 
s bhe purity of the water, temperature, and the nature of the 
J'j’t around which they move. These bodies are frequently 
a ded ova j- but as they are neither ripened by fecundation 
c ri *' enclosed in a special membrane, Mr. Hogg proposes to 
§ * them reproductive gemmules. After becoming once 
they are for ever after incapable of motion, and if they 
^ 0,| ld be removed, rarely, if ever take root again. As soon 
j* 1 they are fixed, there grow from beneath numerous tubu- 
o ° u s fibres, which serve as roots, by which a firmer hold is 
f ained ; and in this state they are better enabled to with- 
an d the violence of the waves. The upper portion of the 
(j^'mules gets elongated, the central pulp enlarged, and 
e first cell is formed. 
pother mode of reproduction is frequently observed in 
a L s anie genera. When a polypidom has been formed from 
f Q S e nimule, the tubular fibres by which the polypidom is 
a .°.* e d frequently trail over a considerable extent of surface, 
<]: as they do so, get enlarged at short and irregular 
tion C - es ; which enlargements increase in an upward direc- 
p 0 | D ’ till, first a stem, then a cell and finally a perfect 
0 | j Jpidom is formed. This mode of reproduction is easily 
0i| S,:rv ed in the Sea-threads ( Laomedca ) so common on 
(pi s hores throughout the year: the Podded Coralline, 
s ’ u mularia cristata,) is another elegant instance of the 
le thing. 
jo^his order then is capable of reproduction; 1st. By the 
g eta n S pullulating from the parent: 2ndly. By reproductive 
enclosed in external vesicles : 3rdly. By shooting 
is s l he tubular roots of existing polypidoms; and 4thly, it 
<li V j ® e times said to occur by division ; as by the artificial 
tin, a t ' 0tl °* the fresh water polypes. Some Authors * in- 
hut this last manner occurs also in the horny genera, 
Ma c lls ^ have never observed, and believe never to take 
off for I have noted that if a branch be either cut 
he 5 c ° r thrown off spontaneously, the utmost it appears to 
a Pable of doing is to survive for a very short time. 
Jones’ Animal Kingdom, p. 47. Sect. 66. 
