178 RITTER. [Vou. XII. 
point of fusion. The permanent hypophysis mouth is there- 
fore in this genus secondary, and not primary as in Goodsiria. 
The groove-like Az/age of the duct in the latter genus is appar- 
ently very similar to that which Kowalevsky (74a), p. 450, has 
described in Didemnium styliferum, the bud-development of 
which resembles that of Goodszria in some other respects. 
B The Ganglion.—The three papers of Oka, Hjort, and Pizon, 
on budding in Botryllus, reference to which has already been 
made, were written so nearly simultaneously that neither author 
was acquainted with the result of the others’ work while prose- 
cuting his own. Jo two of these investigators agree concerning 
the origin of the ganglion, though each was duly impressed with 
the theoretical importance of the question, and was also familiar 
with the discordance in the previous results obtained by several 
investigators who had studied the blastogenesis in various other 
Ascidians. This fact testifies convincingly to the difficulties 
involved in the subject. To these difficulties I too can bear 
witness, and while doing so may be permitted to say that I 
have striven hard to search out every fact that might bear 
on the question, and to draw my conclusions uninfluenced 
by any bias in favor of one or another of the several 
prevailing views. Four different origins have been found for 
the ganglion in the buds of different compound Ascidians 
by different students. 1. It has been derived directly from 
the central nervous system of the parent zooid. 2. It has 
been derived from the free so-called mesoderm cells of 
the body space. 3. It has been derived from the ecto- 
dermic, or outer vesicle of the bud. 4. It has been derived 
from the inner primitive vesicle, or, more precisely, but what 
is the same thing, from the hypophyseal duct. The first was 
advanced by Pizon (93), for Botryllus, evidently suggested by 
the method of origin of the ganglion in the buds of salpa. But 
as the author does not pretend to have proven such a process 
to take place here, and as the facts on which he bases his belief 
are exceedingly meagre, this may be dismissed without further 
remark. 
The suggestion of a mesodermal origin was, so far as I 
know, first made by Seeliger in his studies on Clavelina. It 
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