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that he “ would anyhow make its presence or absence a 
primary character , and therefore follow Hertwig in separating 
from Haeckel’s c Collida ’ those forms which have the nuclear 
vesicle, and uniting them with the other genera which possess 
that structure into a group Vesiculata .” (Memoir, pp. 173, 174.) 
After a prolonged effort to satisfy myself as to what Mr. 
Mivart may mean when using the term “ a nuclear vesicle” 
declared by him to constitute a most important distinction, &c., 
I am constrained to admit that I have given up the task in 
despair. Of course it may be that this is another of the con- 
vertible terms he so frequently employs, and is identical with 
the “ porous membrane called the capsule,” of which we have 
heard so much, which would in that case explain why the term 
nuclear vesicle was so carefully eschewed in the first thirty-six 
pages of his Memoir, inasmuch as it would have been an 
avowal of the non-existence of the declared typical character in 
the most important, widely distributed both in the recent and 
fossil state, and most typical (according to the accepted esti- 
mate) of the Eadiolarian families, the Polycystina , of which I 
have been the persistent advocate. But then Mr. Mivart would 
have had to cancel one of the most important of the structural 
characters which he ascribes to six out of the seven great “ sec- 
tions ” into which he now condenses the fifteen groups of 
Haeckel, and which he embodies always in the three words, 
“No nuclear vesicle.” 
If, however, he employs the term to signify the presence of a 
vesicular nucleolus , within the true nucleus of such forms as 
the Acanthometrce , &c., he certainly appears to me to be 
assuming the presence of a structure in the Bhizopods, which 
does not, under any circumstances, enter into any portion of their 
organization. 
From one short passage in Mr. Mivart ’s Memoir, this would, 
however, seem to be his meaning. For, after referring (at p. 
141) to the intra-capsular sarcode of Thalassicolla , Thalas- 
solampe, and Physematium , which genera alone contain 
“ Alveoli,” he goes on to say that it also “ constantly contains 
one or both of two sets of structures, which structures, according 
to Hertwig, bear to the whole capsule the relation of many 
simple nuclei or of a single complex nucleus to a cell ; ” and 
further, (p. 142,) that “the complex nucleus is a small vesicle, 
the Binnenhldschen or vesicula intima of authors, formed of 
porous membrane similar to, but more delicate than the capsule 
itself.” But even here a new element of confusion is introduced 
by the statement (at p. 162) that “Hertwig considers the 
capsule of Collozoum to be a multinucleate cell or syncytium , 
and agrees with Schneider in thinking that it answers to that 
part of the sarcode of the Foraminifer which lies within the 
