94 Development of the Ovum. By W. 11. Dallinger & J. Drysdale. 
Against Balbiani’s hypothesis — that the nucleus is the ovarium 
and the nucleolus the testis, containing spermatic elements — 
Biitschli affirms that in P. aurelia and P. colpoda the supposed 
spermatic capsule in some cases wholly disappeared without any 
following change in the nucleus that could be discovered, and that 
consequently it did not effect fertilization. In short, he believes 
that the observations he has made are quite competent to overturn 
the sexual hypothesis in these organisms, and to establish that of 
rejuvenescence in its place. 
That there is extreme ingenuity in this hypothesis we readily 
admit ; that there is also the utmost conflict of interpretation 
amongst the best observers of these organisms, we admit with 
equal readiness. But that the author’s observations give scientific 
sanction to his theory on the one hand, or either explain away or 
harmonize the labours of his predecessors or collaborateurs on the 
other, we are fain to dispute. The exhaustive and continuous 
method of observation — following a single form through all the 
phases of its life — has never been thoroughly adopted ; and conflict 
of interpretation inevitably arises. Biitschli has fallen into the 
same groove, and his results, although valuable and full of sugges- 
tion, have no irresistible meaning. They present points of new 
departure for hypothesis, and nothing more. 
Nor can we be quite certain, from the evidence afforded, of the 
correctness of the larger and more important of the facts stated. 
We want, for example, more than a mere statement that the “ciliary 
apparatus ” and the important organs of the peristoma were actually 
destroyed by conjugation. That they are suppressed — flattened — 
deranged by prolonged contact, we have observed again and again 
in several forms, especially Stylonichia, Pustulata, and Mytilus ; 
but they rapidly regained their normal condition, and certainly did 
not grow afresh by “ rejuvenescence ” as in the cases stated by our 
author. And this is certainly of moment. In some important 
sense also this will apply to the nucleus and nucleolus themselves. 
Doubtless the investigations of Biitschli on the metamorphoses of 
these bodies, especially the latter, in such forms as P. bursaria, 
aurelia, putrinum, and others, have a large importance ; and if they 
should be confirmed by continuous observation on the living form, 
controlled by the evidence of preparations, made at short intervals, 
under the influence of acetic and osmic acids, and other reagents, 
not only will Balbiani’s hypothesis become modified, but a sequence 
will be given to the successive stages, often now wanting, in the 
observations of Biitschli himself. It is impossible not to be struck, 
for example, with the minuteness of his observations, made on the 
nucleolus changes in P. bursaria ; but they are utterly incom- 
petent to accomplish his own purpose and establish his own idea, 
lie declares that both Balbiani and Stein utterly mistook the 
