424 Sidney I. Kornhauser 



niust not sliow such a structurei). This is contrary to the facts brouglit 

 forth in the study of Diaptomus, Hersüia, and Lepidosiren. It would 

 also be difficult to understand how the "Querkerbe" could be nearer 

 one end than the other, since it is well known that, with the exception 

 of hetero-chromosomes, the homologous chromosomes which conjugate 

 are always of equal size. Then, too, there would be no syndesis for the 

 chromosome without "Querkerbe", such as the small pair in Hersilia. 



The possibility that the normal number of chromosomes is reduced 

 by an end-to-end union in the primordial germ cells also encounters 

 difficulties, in as mucli as the spermatogonial and oögonial chromosomes 

 would have to appear in reduced number and with "Querkerbe". The 

 faet that, in Cydops fuscus var. distinctus (Amma '11), in Diaptomus 

 coeruleus (Krimmel, '10) and in Hersüia, tlie normal number of chromo- 

 somes with "Querkerbe" have been found in the primordial germ cells 

 speaks against this supposition. We have no evidence that a reduction 

 of the chromosomes occurs in the primordial germ cells. 



It must be admitted that our knowledge as to the origin or signifi- 

 cance of the "Querkerbe" is as yet very incomplete. Not in the Cope- 

 pods alone, however, is such a transverse suture seen; but it occurs also 

 in other groups of animals of which the following are examples: Ascaris 

 canis (Marcus '06); Creseis (Zarnik '11); and Lepidosiren {Agar '11, '12). 

 This light staining crossband in the chromosome, be it a bridge of linin 

 or other substance, is at any rate a constant structure and adds to the 

 evidence that the chromosome is a complex individual. If one examines 

 figures of the second maturation divisions, where the "Querkerbe" is 

 usually most clearly seen (the chromosomes lying with their long axes 

 in the equator), one can he assured that the "Querkerbe" is not a mere 

 Chance break in the chromosome brought about by the fixing agent, 

 but is a part of the structure of the chromosome itself. One might assunie 

 that the "Querkerbe" has originated in the phylogenetic development of 

 the Copepods by the permanent union of the chromosomes in pairs, but 

 against this proposition is the fact that such a "Querkerbe" is also found in 

 the Calanids, the most ancestral of the present-day Copepods. 



B. Syndesis and the Maturation Divisions. 

 As noted in the introduction (pp. 400—401), the copepods have been 

 bound up with the question of equation and reduction divisions, since 



1) Haecker ('10, Y>. 190) says: "Dagegen haben wir bei der Entstehung der Go- 

 naden und speziell in den ovogonialen und spermatogonialen Teihmgen bis jetzt keine 

 sichei-e Andeutung einer Querkerbe angetroffen." 



