STARRY ASCIDIANS. S14 
FAMILY BOTRYLLIDA. 
(Starry Ascidians.) 
The stones that are ordinarily covered by the 
tide, and the coarser sea-weeds, such as the Fucz 
and Laminarie, that grow at low-water, are very 
frequently studded with irregular patches of dark- 
coloured substance, gelatinous to the feel, and often 
somewhat brightly coloured, the more common 
hues being blue, purple, green, grey, and white. 
On closer examination, we find embedded in this 
mass, circles of stars, each consisting of a definite 
number of bright-hued, minute, oblong bodies, 
radiating from a common centre. 
These masses belong to the genus Botryllus, the 
representative of the family before us; and each 
radiating point is an individual animal. From ten 
to twenty of such animals are ordinarily grouped 
together to form one of the wheel-like systems ; 
and there are often as many systems in one en- 
crusting mass. 
The organization of these little animals is in 
general conformable to what has been already 
described; but the discharging orifice of each 
individual is placed at the opposite end from the 
mouth, and opens into the common centre, which, 
rising with a circular rim, expands and contracts 
as a discharging orifice for the whole of that 
system. 
Several species of this genus are common with 
us, one of the most abundant of which is the 
Botryllus polycyclus, which is found encrusting 
the broad leaves of the common Tangle (Laminaria 
digitata). Itis of a bluish purple hue, with the 
individuals marked by white rays. 
