A Cytological Study of the Semi-parasitic Copepod, Hersilia apodiformis etc. 423 



Matscheck '10), and 2) those describing the same (unreduced) nuniber 

 of chromosomes in the spermatogonia or oögonia and in the metaphase 

 plates of the first spermatocytes or oöcytes (Ishikawa '91 ; Steuer '03), 

 the reduction in number taking place in the second niaturation division. 

 But in the above noted works, neither sufficient proof nor convincing 

 figures of the chromosome relations, as described in the text, were given 

 to establish these exceptions, The oöcyte or spermatocyte plates are 

 figured, for they are clear and more nunierous in Copepod material than 

 good diploid groups. 



Agreeing with Hersilia, we have the \Yorks of Krimmel ('10) and 

 Chambers ('12). giving metaphase figures showing that the diploid chromo- 

 some number is present in the spermatogonia and oögonia, while Krimmel 

 ('10) and Amma ('11) extend the facts to the primordial germ cells which 

 also have the unreduced number of chromosomes. Not only is it certain 

 that the diploid number of chromosomes are present in the spermato- 

 gonia, oögonia, and embryonic cells: but it has also been demonstrated 

 that they show the presence of a "Querkerbe". 



The author's observations on Hersilia and Diaptomus coeruleus are 

 supported by the results of Krimmel ('10). Agar ('12) worting on lepi- 

 dcsiren has treated the subject so thoroughly that the present work can 

 add httle to his. He has shown that the transverse constriction or seg- 

 mentation for a given chromosome is a constant structure in a definite 

 Position; and that it is not produced by the union of two chromosomes 

 nor is it the point of Separation in the meiotic phases or embryonic deve- 

 lopment. He has also pointed out that Haecker's ('10) theory of Teleu- 

 tosyndesis can not explain the presence or meaning of the "Querkerbe". 



Even though it l)e somewhat monotonous to find one Single method 

 of niaturation (parasyndesis followed by hetero-homeotypic division), 

 yet the theory of teleutosyndesis is too weakly grounded to aid in under- 

 standing the niaturation phenomena. This theory demands that the 

 homologous maternal and paternal chromosomes unite in pairs, end to 

 end (the "Querkerbe" being the only evidence of such a union), and in 

 niaturation pass through two longitudinal (equation) divisions. Each 

 chromosome of the gamete is half maternal, half paternal. In the forma- 

 tion of a ncAV individual, the chromosomes which are brought together 

 by a union of two germ cells must show a "Querkerbe", which in the later 

 development of the organism (earliest, in the formation of the sex glands) 

 must disappear through the complete fusion of the maternal and paternal 

 components of each. If the "Qerkerbe" is fornied by metasyndesis in 

 the growth period, then the oögonial and spermatogonial chromosomes 



