Ao6 LEFEVRE. [Vou. XIV. 
(8) The sexual organs have a common origin from free 
amoeboid blood cells, both testis and ovary arising from one 
and the same spherical rudiment. 
Concluding Remarks. 
The results which I have obtained from the study of the 
budding of Perophora viridis furnish additional evidence in 
support of the view that the development of the bud and that of 
the embryo do not proceed along parallel lines. The attempts 
which have been made to harmonize the facts of budding with 
the germ layer theory have been totally futile in the case of 
ascidians, and any hypothesis which explains budding in the 
ascidians as a process of regeneration, by which the organs of 
the parent, or their germ layers, give rise to similar organs in 
the bud, must, in the light of known facts, be ruled out. 
The rudiment of the bud in all groups of compound ascidians 
is composed of two vesicles, one within the other, enclosing 
between them free cells of the blood. The outer vesicle is always 
derived from the ectoderm of the parent, and gives rise to the 
ectodermal covering of the bud. The origin of the inner vesicle, 
however, is not the same in all ascidians. In the Botryllidae 
it arises, in both embryozodid and blastozodid, from the peri- 
branchial wall, which is formed in the first place from the 
ectoderm of the embryo. This vesicle is, therefore, ultimately 
of ectodermal origin in Botryllus, whereas in all other ascidians 
it comes from an endodermal structure of the parent. Although 
derived in the two cases from different germ-layers, the inner 
vesicle may go to form the same organs in the bud but organs 
which are of widely different origin in the larva; for example, 
the digestive tract and nervous system (Hjort, Botryllus (8), 
Distaplia (10), Glossophorum (g)). It is, therefore, perfectly 
evident that the fate of the inner vesicle entirely precludes the 
application of the “‘germ-layer theory”’ to the ascidian bud. 
In Perophora viridis the important part played in the bud 
development by cells of the blood only increases the disagree- 
ment. Organs which in other ascidian buds arise from either 
ectoderm or endoderm are here formed by the coming together 
