222 RITTER. [Vor. XII. 
In GENERAL. 
1. It is now established beyond question that in some, at 
least (and Goodsiria may be taken as one of the best instances 
of this), of the Compound Ascidians the outer layer of the bud 
contributes much less to the structure of the adult blastozooids 
than it does to the adult embryozooids. This is most conspicu- 
ously seen in the case of the nervous system, for this is cer- 
tainly produced from the outer, or ectodermic layer, of the 
embryo, while it is as certainly produced from the inner layer 
of the bud. Whether we call this inner layer endoderm or 
not, the fact of chief importance remains that the same layer 
produces most of the organs of the zooid, among which are 
included the digestive tract and the nerve ganglion. 
2. The anomalous course of development of the bud is due 
to the fact that the ectoderm is at no time in the life of the 
bud an undifferentiated, or embryonic layer. It is from the 
very outset and always a fully formed organ, its function 
being to secrete the cellulose matrix of the test. The inner, 
or endodermic, vesicle of the bud is, on the other hand, in the 
completest sense, an undifferentiated, or embryonic layer. By 
this purely physiological cause the inner layer has been made 
to produce structures, most important of all the nervous 
system, which in the embryo are produced by the ectoderm. 
3. Illustrations of the potency of physiological influences to 
profoundly change the usual course of development are found 
in the budding of other animals, one of the most instructive of 
which is the medusa Rathkea octopunctata, where the change 
has been in the opposite direction from that in the Ascidians ; 
for here the endoderm takes no part in the formation of the 
bud, the whole blasto-medusa being produced from the maternal 
ectoderm. 
4. The evidence now in hand, drawn from adult structure 
and from the blastogenesis strongly tends to the conclusion 
that the budding of Goodsiria and Botryllus, represents a type 
that is genetically independent of the type represented by 
Perophora. In other words, that the type of budding rep- 
resented by Goodsiria, has originated independently of the 
