400 Sidiiey I. Kornhauser 



I. Introduction. 



The followiiig study deals in tlic niain with tlie spermatogenesisi) 

 of HersiUa apodiformis (Phil.), and lays special emphasis upon the 

 method of syndesis and the presence of a "Querkerbe"^) in the chromo- 

 somes. Various phenoniena in the oögenesis and cleavage cells will be 

 described also to Supplement the observations on the spermatogenesis ; 

 and a pair of lagging chromosomes, whose behavior resembles that of 

 the paired "sex-chromosomes" of the Nematodes and Insects, will be 

 considered under the spermatocyte divisions. 



At this point I would like to express my gratitude to Professor V. 

 Haecker for the courtesies extended to nie during my stay at his 

 laboratory, to the Direction of the Zoölogical Station at Naples for the 

 procurrence of a large amount of material, and to Professor Theodor 

 ßovERi for his many valuable suggestions in the study of HersiUa and 

 for the opportunity of working in his Institute. Also to Privatdocent 

 Dr. B. Zarxik am I indebted for helpful criticisms which aided in the 

 preparation of this work. 



II. Review of Previous Literature. 



During the past twenty years numerous papers have appeared dealing 

 with the maturation phenoniena in the oögenesis of the Copepoda. The 

 principal efforts of the earlier investigators (Ishikaw^a '91; Rückert 

 '94a, '94b; Haecker '95a, '95b; vom Rath '95) were made to test the 

 reality of the postulations of Weismann and the main questions were: 

 (1) Is there a reduction of the normal (somatic) chromosomal nuniber 

 in the maturation divisions? (2) Is the first or second maturation divi- 

 sion that which separates the chromosomes into qualitatively different 

 groups (reduction division), or are both divisions reductional? 



That the Copepods, in spite of the clearness of the chromosomes in 

 the maturation spindles, w^ere not the most favorable group for a simple 

 Solution of these problems is due: (1) to the difficulty in obtaining good 

 oögonial or spermatogonial metaphase plates for counting the chronio- 



1) The scarcity of literatiire on the spermatogenesis of Copepods is doubtless 

 due to the fact that the material is very difficult to fix without considerable shiinkage. 

 For a further consideration of this point see footnote, page 8. 



2) "Querkerbe'' — a term first used by Haecker ('95b) to denote a Jight stain- 

 ing transverse streak, appearing in the chromosomes of the maturation divisions of 

 Cyclops Irevicornis. 



