Vol. XXV. October, 1913. No. 5 



BIOLOGICAL BULLETIN 



SIZE DIMORPHISM IN ADULT SPERMATOZOA OF 



ANASA TRISTIS. 1 



E. C. FAUST. 



I. INTRODUCTION. 



The work on which this paper is based was undertaken with 

 the object of determining the existence or non-existence of size 

 dimorphism in the mature spermatozoa of Anasa tristis. Sper- 

 matogenesis studies of this form have shown that one half of the 

 spermatozoa receive one more chromosome each than the other 

 half. A corresponding difference in size of the mature sper- 

 matozoa may therefore be expected. 



The study was carried on during the academic year 1912-1913, 

 under the direction of Professor Charles Zeleny, to whom my 

 thanks are due for his many valuable suggestions. 



II. MATERIALS AND METHODS. 



I. General Account. The material used in this study was 

 collected from two localities, Urbana, 111., and Bradford, N. H., 

 during the month of October, 1912. The testes of these indi- 

 viduals were teased out in normal salt solution and made up into 

 temporary and permanent smear preparations. 



Smears of adult spermatozoa were prepared by the aceto- 

 carmine method and by the osmic-haematoxylin method. In 

 addition intra miam staining was tried, but without success. 

 The first mounts were made up as aceto-carmine preparations. 

 Although this affords an excellent preparation for the study of 

 spermatogenesis, it is not a good method to use in the study of 

 adult spermatozoa. Curling is frequent. Distortion by swelling 



1 Contributions from the Zoological Laboratory of the University of Illinois, 

 under the direction of Henry B. Ward, No. 23. 



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