The germ-cells. 689 



sary number of divisions of the germ-cells, their ripenings, and their 

 new conjugations ? 



At this point it is fitting to indicate how closely the line of 

 thought of the present chapter reseml)les certain ideas and doctrines 

 enunciated by Weismann long ago. Three of his essays, published in 

 1882, 1883, and 1884, with the respective titles "Die Dauer des 

 Lebens", "Ueber die Vererbung", and "Ueber Leben und Tod", con- 

 tain, among the wealth of ideas, which characterises them, conceptions 

 so like some of those of the present chapter as almost to raise a 

 suspicion of plagiarism. 



That there is no plagiarism on my part will, I trust, be quite 

 clear from the circumstance, that at the time, when Weismann's essays 

 were written, our knowledge of the life-cycle of a germ-cell, that is, 

 of the ripening processes, reduction of chromosomes, etc., was not 

 such that any real valid comparison of them with unicellular organisms 

 could be made. 



It is, however, on the complete homology of germ-cells and uni- 

 cellular organisms and on the close correspondences of their life- cycles 

 that my conclusions are based. On this conception of the germ-cells 

 as unicellular organisms the consequences I have drawn seem to follow 

 as a matter of course. 



Although Weismann has long foreseen and insisted upon the im- 

 mortality of the germ-cells and their resemblance to the unicellular 

 organisms in this respect, one searches in vain in his writings for a 

 recognition and acknowledgment of the germ-cells as unicellular or- 

 ganisms. 



On p. 22 of the third essay he even speaks of the germ-cells 

 as surrounding themselves with a soma, a point also developed in 

 the present chapter. 



On the other hand, his conception of the cycle of the individual 

 development differs in toto from that, which my work of the past 12 

 years and more has forced me to adopt as the only true one ^). And, 

 as previously mentioned, he maintains in many cases at least the 

 possibility of somatic cells becoming germ- cells. 



My conclusions as to the germ -cells, in so far as they are con- 

 tained in the present chapter, though based on other facts and 



1) As elsewhere already written, ''direct development" in the Meta- 

 zoa is as much an impossibility as epigenesis, or as the formation of 

 germ-cells from somatic cells. 



