180 RITTER, [Vot. XII. 
accumulation of cells in the blood space between the already 
formed hypophyseal tube and the walls of the branchial 
and peribranchial sacs. This becomes more compact and 
regular in form; in short, it develops into the ganglion. 
Concerning the origin of the cells composing the mass, the 
author’s essential words are: ‘“ Was die Herkunft dieser Zellen 
betrifft, so entstammen sie der Korperwand und zwar gehen 
sie durch Proliferation des dorsalen, oberhalb des hypophysaren 
Rohres gelegnen Epithels hervor (Fig. 33). Dzeser Vorgang 
... kann nur in giinstigen Fallen beobachtet werden, denn die 
Zellen verlieren sehr rasch den Zusammenhang mit den Epithel- 
zellen, von denen sie sich abspalten, und wandern einzeln oder 
gruppenweise rechts und links um das Rohr herum und sammeln 
sich an der unteren Seite desselben” (p.540). The italics are 
mine, employed because these are to me the most significant 
words of the description. No one who has had experience in 
studying such a process as the author here so briefly describes 
(for the quotation contains all he has to say on the point) will 
be convinced by the evidence which he has produced that he 
has not fallen into error. Only a single figure illustrates his 
statements, and while in this two cells are shown which 
undoubtedly appear as though they might be in the act of 
leaving the ectoderm to enter the blood space, still in the 
absence of further illustration, or more precise statement, this 
instance cannot appeal to one as being necessarily more than a 
deceptive appearance. 
The inadequate support produced by Oka for his view, 
together with the fact that he is opposed by all other observers 
(Della Valle, Hjort, and Pizon, who have studied the point in 
Botryllus), and likewise by my own results in Goodstria, compel 
me to reject his conclusions. 
Concerning the ectodermal origin of the ganglion in Clavelina, 
it is worth while to point out that Von Beneden et Julin have 
not given the subject special attention in their paper. Under 
the topic, “Development du coeur etc.” they incidentally 
mention the ganglion several times, and it is shown in numerous 
figures ; in most of them in close contact with the ectoderm, 
but also in most quite distinct from it. However, figures 

