No.1.] BUDDING [IN GOODSIRIA AND PEROPHORA. 211 
of its own food, for it is entirely bathed in the maternal blood. 
It is relieved from all offices except to assimilate already 
digested food, and to grow. 
Why should not the production of structures which in the 
embryonic development belongs to the ectoderm be here trans- 
ferred to the endoderm? And soitis. This conclusion is the 
more justified when it is considered how different are the con- 
ditions under which the two layers develop in the embryo. 
Here the neural canal is formed while yet the ectoderm is 
strictly an embryonic structure, and before the endoderm 
(particularly in the compound Ascidians, e.g. Amaroeciui, 
Maurice et Schulgin, 'g4) is differentiated from the richly laden 
yolk cells which ultimately give it origin. 
We have here an instance where physiological requirements 
have run counter to the course in which, through heredity 
alone, development would proceed; and the former have 
proved more powerful. To my mind the chief difficulty in 
such a case is not that developmental conditions can so pro- 
foundly modify the usual course of things, but that by such 
different courses precisely the same result should be reached. 
In Perophora, for example, no one has detected any difference 
between the adult embryozooid and the adult blastozooid. The 
same is true of C/avelina, and this case is more important, 
perhaps, because the embryology of this genus has been very 
thoroughly studied up to the practically adult state. 
It appears certain that heredity has here an w/¢¢mate aim, as 
we may call it, and that it is able to reach this even though 
it be thrown considerably off its regular course by special func- 
tional requirements ; in other words, that heredity is prospective. 
In this connection one may refer to the fact that in some 
compound Ascidians, e.g. Botryllus, there is no such thing as 
an adult embryozooid, and the suggestion may be made that 
the much abbreviated life of the embryozooid in such instances 
is in some way correlated with the profound modification 
undergone in the development of the blastozooid as compared 
with the embryozooid. 
I have already pointed out on another occasion ('95a) that at 
least one other instance of anomalous bud origin may receive 
