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On the Occurrence of Certain Ciliated Infusoria within the Eggs 
of a Rotifer, considered from the Point of View of 
Heterogenesis. 
By H. CHaruiton Bastian, M.A., M.D., F.RS. 
(Received February 14,—Read March 16, 1905.) 
(PLATE 7.) 
(Abstract.) 
The weight of preconceptions against the possibility of the occurrence of 
Heterogenesis has hitherto been so strong as to have made it almost 
impossible to obtain any adequate consideration for the actual evidence 
adduced in favour of this or that alleged instance. But of late, preconcep- 
tions in the domain of physics and chemistry have received severe shocks, 
and when we are told that a so-called “element ” is daily being transformed 
and another is actually originating therefrom, there appears more chance of 
attention being paid to the alleged existence of phenomena in the organic 
world which would seem to be but the carrying on into a higher platform 
of the familiar but important phenomena known as allotropism and 
isomerism. 
Hitherto, alleged instances of heterogenesis have, without adequate 
consideration of evidence, been almost always assumed to be results of 
“infection,” but the writer claims that in the cases with which the present 
article is concerned, any such explanation is quite impossible in regard to 
one of the cases, at least, in which we have masses of living matter so large 
that they average } mm. in diameter, being converted in the course of three 
days into great Ciliated Infusoria of equal bulk. 
The communication deals with two sets of heterogenetic transformations 
occurring in the great eggs or “gemme” of one of the largest of the 
Rotifers, namely, (1) the transformation of the entire contents of a 
Hydatina egg into a single great Otostoma; and (2) the segmentation of the 
Hydatina egg into 12 to 20 spherical masses, and the development of these 
sometimes into enbryo Vorticellze, and sometimes into embryo Oxytriche. 
Rotifers and Ciliated Infusoria belong to such distinct phyla of the animal 
kingdom that no immediate kinship can possibly obtain between them, and con- 
sequently heredity, in the ordinary sense of the term, can have nothing to do 
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