Development of the Ovum. By W. H. Dallinger & J. Drysdale. 91 
example, he admits that the transition of the nucleus spindle into 
the “ Richtungsblaschen ” cannot be made out as in Nephelis, but 
contends that it ought not to he doubted. And precisely the same 
difficulty attaches to the transformations of the nucleus, of which 
“ nothing could be certainly found yet the same doctrine is 
carried over, as though precisely the same phenomena had been 
witnessed as in Nephelis. So in relation to other Nematoids, it is 
rather inference than evidence that the protruded vesicle is the 
germinal vesicle, as in Nephelis. So in Limnseus auricularis, 
essential points in the original and subsequent evolution of the 
spindle and nuclei are presented, not as the result of observation, 
but of inference, and a leap across a chasm between two prepara- 
tions of the ovum which show no continuity of evolution, is taken 
with an assurance that “doubtless,” although the intermediate 
process was not made out, we might be guided by the analogy of 
Nephelis. 
These facts are pointed out, not in the slightest degree to 
detract from the value of the author’s observations, but simply 
to separate them, as such, from the inferences he draws from them. 
There can be little doubt that great value belongs to the discovery 
of the nucleus spindle and its behaviour in evolution ; and there 
can also he little question that it is largely original research ; but its 
relation to anterior and subsequent processes is not so definitely 
discovered. It is nevertheless a source of great interest to find that 
Balbiani has given such complete and recent confirmation to the 
main characteristics of the spindle nucleus.* It is true that he 
does not confirm the division of the equatorial band in the nucleus, 
and claims to have shown the existence of the clear spaces and 
rayings accompanying the nucleus transformations in the eggs of 
spiders four years before. But evidently a step is gained by these 
observations on the earliest development of the ovum ; although, 
from the careful work of M. Fol, it is clear that not only the inter- 
pretation, but the detail, may be open to question. t 
Coming now to the large and important question of the Con- 
jugation of Infusoria, its nature and bearing upon the life-history 
of the forms, we are bound to state at once our conviction of the 
inefficiency of the observations recorded on account of their dis- 
continuity. Nothing but a close and continuous observation of the 
same forms extending over an entire life cycle, repeated again and 
again, can lead to absolute results. Errors fatal to the interests of 
truth inevitably arise, when minute organic forms are studied, not 
by continuous watching, but from inferences made from the phe- 
* “ Sur les Phenomenes de la Division du Noyau Cellulaire,” ‘ Comptes 
Rendus,’ Oct. 30, 1876. 
t “ Sur les Phe'nomenes Iutimcs de la Division Cellulaire,’’ ‘ Comptes 
Rendus,' Oct. 2, 1876. 
VOL. XVIII. 
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