192 Harry Lewis Wieman. 



predecessor. In this way the genetic continuity of the chromo- 

 somes is preserved in the resting stages, "Eine genetische Con- 

 tinuitat der Chromosomen nacheinanderfolgenden Mitosen konnte 

 in der von mir untersuchten Objekten teils sicher (Alium, Amphi- 

 uma) teils mit iiberwiegender Wahrscheinhchkeit {Ascaris) ver- 

 folgt werden. Es ging aber auch hervor, dass eine Identitat der 

 Chromsomen verschiedener Mitosen nicht existiert, sondern 

 dass jedes Chromosom in einem friiher existierenden Endogen 

 entstanden ist, um wieder am Ende seines Lebens fiir die endogene 

 Entstehmig eines neuen Chromosoms die Grundlage zu bilden" 

 (p. 54). 



Overton ('09) claims that in the somatic nuclei of Thalistrum 

 purpurascens and Calycanthus floridas the chromosomes are 

 represented during the resting stage by definite, visible bodies; 

 the pro-chromosomes, which are arranged in parallel pairs with 

 apparent linin intervals. Prochromosomes are also present in 

 the resting nuclei of the germ cells of these plants and Richardia 

 africana, in exactly the same arrangement and form as in the 

 somatic nuclei. The homologous parental elements are already 

 associated in pairs when they enter the reconstruction stage of 

 the germ nuclei. 



The results of these two investigators will serve to indicate 

 the increasing evidence in favor of permanence of the chromo- 

 somes, which is to be held distinct from the idea of automatism 

 in these bodies. 



In the spermatocyte of L. signaticollis, when the spireme of 

 the synizesis stage enters the rest stage showing a definite arrange- 

 ment of its segments, and later emerges from that stage showing 

 the same arrangement of parts, it is obvious that the organiza- 

 tion which is responsible for this configuration must have persisted 

 in some form through the intervening rest period; even though the 

 outlines of the chromosomes and spireme are temporarily lost to 

 view. In other forms where the evidence for prochromosomes is 

 relatively clear, the existence of this organization is more apparent ; 

 but even here the chromosomes undergo a kind of vacuolization or 

 disintegration, leaving but a mere skeleton to indicate their 

 presence. In other words, each chromosome on entering the 



