Biologisches Gentralblatt 



Unter Mitwirkung von 

 Dr. K. Goebel und Dr. R. Hertwig 



Professor der Botanik Professor der Zoologie 



in München, 



herausgegeben von 



Dr. J. Rosentlial 



Prof. der Physiologie in Erlangen. 



Vierundzwanzig Nummern bilden einen Band. Preis des Bandes 20 Mark. 

 Zu beziehen durch alle Buchhandlungen und Postanstalten. 



Die Herren Mitarbeiter werden ersucht, alle Beiträge aus dem Gesamtgebiete der Botanik 

 an Herrn Prof. Dr. Goebel, München, Luisenstr. 27, Beiträge aus dem Gebiete der Zoologie, 

 vergl. Anatomie und Entwicklungsgeschichte an Herrn Prof. Dr. R. Hertwig, München, 

 alte Akademie, alle übrigen an Herrn Prof. Dr. Rosenthal, Erlangen, Physiolog. Institut, 



einsenden zu wollen. 



XX1TI. Bd. 15. Januar 1906. M 2. 



Inhalt: Henriksen, A Functional view of Development (SchlussV — Schimkewitsch, Die Mutations- 

 lehre und die Zukunft der Menschheit. — Versluys, Über die Konjugation der Infusorien. 

 — Zacharias, Die Begründung zweier neuer Süsswasserforschungsstationen im Auslande. — 

 Zacharias, Ein schwimmendes Laboratorium für marine Biologie. — Molisch. Die Licht- 

 entwickelung in den Pflanzen. 



A Functional view of Development. 



Everything in nature tends to wards a state of equilibrium 

 which is peculiar to itself. 



(Schluss.) 



We will now discuss some of the experiments on the earlier 

 embryological stages and see how they can be interpreted from 

 this point of view. 



The fact that the growth energy is lessened in an arithmical 

 ratio as to the part of the egg used, that is, if we use an isolated 

 blastomere of the sixteen cell stage we get an embryo of one- 

 sixteenth the normal size, andif an isolated blastomere of the two-celled 

 stage, or a non-nucleated part of the egg is fertilized by a sperm, 

 or an egg by artificial Stimulation is made to develop; in all cases 

 we get a larva of but half the size of the normal one, show that 

 this growth-energy, which determines the size of the larva lies, in 

 these cases at least, within the nucleus. 



But it is not always we can hold our stand and say that after 

 Separation each blastomere acts as a whole egg; but in every case 

 we can say that changed relations, as Separation, of the balstomeres 

 tend toward establishing the equilibrium of the species. In other 

 words the relations within the blastomeres of two or four cell 

 XXVI. 3 



