E. YUNG — INFLUENCE DE L'ALIMENTATION 297 
As this condition is seen abundantly in all early gastrulæ, and as there 
are no temporary annexes of the embryo which these amitotic nuclei 
could form, one is compelled to recall the belief that mitosis is rather 
useful expression rather than a necessary mechanism of metabolic 
activity. 
Seventh: In provision for the more effective nutrition of the embryo 
during later stages. Here particularly is to be referred the taking up of 
nutriment by the embryo via external gills and gut. In the shark the 
yolk material nourishes the embryo largely if not entirely by umbilical 
vessels. In Chimæra, on the otherband, the umbilical mode of nutrition 
is less conspicuous since the yolk sac is of miniature size. A large part 
of the egg, it is found, is not enclosed by the down growing blastoderm. 
And this larger part of the egg, on the other hand, undergoes a process 
of fragmentation (which follows repeated division of the yolk nuclei), 
resulting in the production of a creamy fluid which bathes the embryo 
and in which, therefore, the external gills are freely exposed. Interesting 
accordingly, is the fact that in the gill filaments are found at various 
points large blood knots in which numerous hæmacytes are found 
undergoing division. It may be mentioned also that for a considerable 
period the yolk laden ventral wall of the gut buds off directly into the 
gut lumen many small yolk masses, which, judging from mitoses in the 
adjacent wall of the gut, are of nutritive value. These conditions, it may be 
mentioned, are, as far as is at present known, uniquein the vertebrateline. 
De l'inifluence de l'alimentation sur la longueur de l'intestin. 
Expériences sur les larves de Rana esculenta. 
Par le prof. E. YUNG (Genève). 
Je renvoie pour l'historique de la question et la bibliographie au ré- 
cent travail de Edward BaBar ‘. Je rappelle seulement qu’on admet géné- 
ralement une influence de la nature de la nourriture sur la longueur de 
l'intestin des animaux; Celui-ci atteindrait son maximum de longueur 
chez les herbivores et son minimum chez les carnivores. Les omnivores 
tiendraient à cet égard le milieu entre les deux groupes précédents. De 
fait, l'observation tout en confirmant d’une manière générale cette règle, 
! Ed. BaBax. Ueber den Einfluss der Nahrung auf die Länge des Darmkanals. 
Biolog. Centralblatt, Bd. XXII, p. 477-483 et 519-528, 1908. 
