90 ASCIDIANS CHAP. 
united in little groups which are connected by stolons. The last 
genus contains one species, Ch. reticulatus, in some respects a 
transition-form between the other Polystyelidae and the Styelinae 
amongst Simple Ascidians. 
Budding in Holosomata—lIn the Polystyelidae, according to 
Ritter! the budding is of the same type as in Botryllidae, the 
bud arising in each case from the lateral body-wall of the parent. 
In Botryllus” the oozooid formed from the larva gives rise at 
a very early period to the first blastozooid of the future colony. 
This then forms the two buds of the second generation on its 
sides (see Fig. 55), and these in their turn form the third, and 
these the fourth generation, in which there are thus eight blasto- 
zooids ; and so the process goes on, the buds of each generation 
arranging themselves in a circle to form 
a system. As each new generation 
makes its appearance, the preceding one 
undergoes degeneration, and is eventu- 
ally absorbed. Consequently, in a system 
there can usually be seen, in addition 
to the adult members, certain older 
ones in various stages of degeneration 
and removal, and certain younger ones 
Fic. 55.—Diagram to illustrate arising as buds on the sides of their pre- 
he ee ee AoE he decessors, or just separated from them, 
oz, oozooid ; Bl 1, first and ready to take their places as young 
pape ene eeane ascidiozooids in the system. Three dis- 
tinct generations are thus commonly 
seen in a system. Now and again one or two young ascidio- 
zooids become squeezed by the pressure of their neighbours out 
of a system into the surrounding test, and so give rise to new 
systems which add to the extent of the colony. 
Sub-Order 3. Ascidiae Luciae. 
Free-swimming pelagic colonies having the form of a hollow 
cylinder closed at one end (Fig. 56). The ascidiozooids forming 
the colony are imbedded in the common test in such a manner 
that the branchial apertures open on the outer surface and the 
1 Journ. Morph. xii. 1896, p. 149. 
2 See Pizon, Ann. des Sci. Nat. 7° sér. Zool. xiv. 1892. 
