Biologisches Centralblatt, 



Unter Mitwirkung von 



Dr. K. Goefoel und Dr. R. Hertwig 



Professor der Botanik Professor der Zoologie 



in Miinchen, 



herausgegeben von 



Dr. J. Rosentlial 



Prof, der Physiologic in Erlangen. 



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

 Zu bezielien durch alle Buchhandlungen und Postanstalten. 



XXII. Band. i. Juni 1902. Nr. 11. 



In halt: Beard, Heredity and the epicycle of the germ-cells. - - Marcs, Das Energie- 

 prinzip und die energetische Betrachtungsweise in der Physiologic (Schluss). 

 Schall'cr, Eine Sperrvorrichtung an den Zehen des Sperlings. 



Heredity and the epicycle of the germ- cells 

 by J. Beard, D. Sc., 



University Lecturer in Comparative Embryology, Edinburgh. 



Owing mainly to the writings of Brooks, de Vries, 0. Hert- 

 wig, Nageli, Herbert Spencer, and above all others, Galtoii 

 andWeismann, the problems of heredity have occupied a prominent 

 position in the scientific discussions of recent years. 



The progress of research into the life-history of the cell, the struc- 

 ture and functions of the nucleus, the phenomena of cell-division, more 

 especially those of the ,,ripening" of the ,,sexual products", have 

 naturally played important parts in these. Indeed, so much has this 

 been the case, that H. F. Os born might well say ,,the study of here- 

 dity will ultimately centre around the structure and functions of the 

 germ- cells". 



It is not my intention to attempt the task of writing a history -of 

 these discussions and theories: what is proposed is merely to indicate 

 the broad and obvious bearings of certain of my results, relating to 

 the history of the germ-cells, on the general problem of heredity. 



In order to obtain a clear insight into the process or processes, 

 by which in a wide sense germinal continuity, resulting in the phe- 

 nomena of heredity, is brought to pass, it is a requisite postulate, that 

 an uninterrupted and continuous panorama of the whole course of deve- 

 lopment from one generation to the next should be secured. Heredity 

 must be dependent on some sort of germinal continuity ; whether of a 

 special germ-plasm in Weismauu's sense, or a consequence of an 

 uninterrupted sequence of germ-cells, or a result of an iutracellular 

 pangenesis, or something else. 



XXII. 21 



