THE SPERMATOGENESIS OF UMBRA LIMI WITH 

 SPECIAL REFERENCE TO THE BEHAVIOR 

 OF THE SPERMATOGONIAL CHROMO- 

 SOMES AND THE FIRST MATU- 

 RATION DIVISION. 



JAMES O. FOLEY, 

 ZOOLOGICAL LABORATORY, UNIVERSITY OF WISCONSIN. 



INTRODUCTION. 



Recent advances in the genetics of the Teleosts have given 

 an impetus to the study of the chromosomes of fishes. The 

 discovery of an XX, XY type of sex-linked inheritance in Lebistes 

 reticulatus (Schmidt, '20; Winge, '22), Aplocheilus latipes (Aida, 

 '21) and Platyposcilus (species?) as studied by the writer, 1 indi- 

 cating an XX, XO type of sex-linked inheritance, all point to 

 the presence of heterochromosomes in the fishes, although none 

 have as yet been recorded. Winge ('22) suggests the possibility 

 of such elements existing in Lebistes but gives no cytological 

 evidence. Geiser ('24) says in discussing the subject in Gambusia, 

 "If one were to trust to the uncertain help of analogy, it might 

 be claimed that Gambusia has one heterochromosome." Agar 

 ('n) shows in the heterotypic division of Lepidosiren paradoxa 

 (although he does not indicate them as such), two large chromo- 

 somes, almost identical as to size and shape. These chromo- 

 somes show a tendency to behave like the sex-elements in those 

 forms in which they have been definitely worked out. The 

 nature of these chromosomes and their similarity of size and 

 shape would seem to indicate, if they are sex-chromosomes, that 

 in Lepidosiren the male is homozygous for sex and should show 

 the poultry type of sex-linked inheritance. 



Upon reviewing the literature on the spermatogenesis of the 

 Teleosts, it becomes apparent that there are many features 

 in the germinal cycle of these forms which are not clear, and 

 that these should be studied further before proceeding with the 

 problem of the sex-chromosomes. During the summer of 1923 a 



1 Data as yet unpublished. 



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