No.1.] BUDDING IN GOODSIRIA AND PEROPHORA. 195 
3. PERICARDIUM AND HEART. 
It appears to be the rule that the pericardium is the very 
first organ to be founded in the Pevophora bud. At least, I 
have found a structure present in several buds at a time when 
the primitive inner vesicle is still wholly unmodified, which I 
suppose to be the Axdage of this organ. One of these is 
“epresented im) Figs.; 67 and 68, Pl. XVI. 
My reason for thinking this to be the beginning of the peri- 
cardium is this: the sections of this bud are cut from the 
posterior toward the anterior end of the future zooid, conse- 
quently they are seen in their natural position as regards right 
and left. This, as I have pointed out a few pages earlier, 
makes this structure in the position, the slight lateral rotation 
of the vesicle to the right having been performed, that the 
heart occupies in the adult bud. The only question that could 
be raised against this identification would rest on the possi- 
bility, first, of error concerning the anterior and posterior ends 
of the bud; and second, that in this instance we have an 
exception to the rule that the septum is connected with the 
left peribranchial sac. As regards the first, the possibility of 
error is remote because another older bud in the immediate 
vicinity is clearly cut from behind forward, and the two are so 
close together that a reversal of their anterior ends is hardly 
possible. As regards the second, nothing can be said beyond 
what was asserted in discussing the relation of the bud to the 
stolon ; vzz., that in the large number of buds observed, no 
exception to the rule has been found. If this is an exception, 
it is the only one hit upon. 
We may then regard it as certain that the cell mass under 
consideration is the Az/age of the pericardium. The origin of 
it is a difficult matter to decide. The numerous and widely 
separated groups of Tunicates in which the pericardium has 
been satisfactorily shown to arise from the endoderm is a 
circumstance that in itself makes its similar origin here 
probable ; and my observations on the whole point in the same 
direction, though I have been unable to remove from my mind 
some traces of doubt on the subject. As shown in Fig. 68, 
