

1905, | the English Species of Nummulites, ete, 315 
by MM. Lemoine and R. Douvillé, Sur le genre Lepidocyclina (12), a copy of 
which I owe to the courtesy of the authors. Written as this memoir has 
been in close association with M. Schlumberger, who in the fine series of 
papers on the structure of the tests of the Miliolide and other forms has done 
so much, either alone or in conjunction with M. Munier-Chalmas, to establish 
the dimorphic character of the tests of the species of foraminifera, the views 
herein expressed carry the greater weight. On p. 7 we read, under the 
heading Dimorphisme :— 
“ Chez les Orbitoides, comme chez la plupart des Foraminiféres on trouve 
deux séries, une forme A & mégasphére, une forme B a microsphere. On sait 
maintenant par les observations de Schaudinn et par celles de Lister que ce 
dimorphisme est di dans certains cas* & un phénomene de génération alternante. 
La forme mégasphérique donne, par sporulation, des zoospores; ces zoospores 
se conjuguent, et le produit de leur conjugaison, en se développant, donne 
naissance 4 la forme microsphérique. Celle-ci par bourgeonnement redonne 
des formes mégasphériques. 
“Le cycle n’a d’ailleurs jamais été suivi complétement. [I] est trés probable 
que les formes mégasphériques ou microsphériques peuvent se reproduire 
directement l’une ou l'autre, sans passer par la forme alternée. Nous ne 
savons rien des conditions de milieu que déterminent la prédominance par- 
tielle ou totale de l’une ou Il’autre de ces formes ; mais, ce qui est certain, c’est 
que ces deux formes couplées n’ont qu’exceptionnellement la méme extension 
verticale.” 
This last passage not only emphasises the view temporarily held, and, as 
we have seen, abandoned by de la Harpe, of the occurrence of solitary forms 
in certain beds, but goes far to undermine his law of the association of 
species, for which there is such abundant evidence. 
From the facts of the life-history now known to us, such a phenomenon as 
the authors describe would mean, if we are to take the vertical distribution of 
the species in every case as the unaltered record of the phenomena exhibited 
by it during the period in which it inhabited a given locality, that either at the 
beginning or the end of that period, or at both, only one phase was present in 
the life-history, while at another part of that period the species became or 
had been dimorphic. 
But the phenomenon was, I believe, well known to Munier-Chalmas and 
attributed by him to a redistribution of the materials of a bed under the 
action of currents—the coarser fragments being deposited here and the finer 
elsewhere. And until such an explanation has been excluded it is surely 
* The italics are the authors’. 
