THE DEVELOPMENT OF THE APYRENE SPERMATOZOA OF 

 STROMBUS BITUBERCULATUS. 



By Edwin E. Reinke. 



INTRODUCTION. 



The fact that there is a dimorphism in the male sex cells of many Proso- 

 brachs is well known at the present day. This is due to the great number 

 of investigations that have been directed to the subject, but, in spite of 

 them all, we are still as much in the dark as regards the function of the 

 atypical spermatozoa as were the earlier investigators who did their work 

 more than half a century ago. Furthermore, while the list of Prosobranchs 

 in which this dimorphism obtains has been extended to a great many forms, 

 in only a few of them do we have careful descriptions of the structure of 

 the atypical spermatozoa, and in only one case (Paludina) is there a complete 

 account of their development. 



Obviously the solution of the problem is to be sought in a study of as 

 many forms as possible, for I believe that each form has not only its own 

 peculiarity in structure, be it great or small, but also its peculiarity in 

 development. By peculiarity I mean not only the differences in form and 

 size and in development between the typical and the atypical spermatozoa 

 of any one genus, but also the differences between the atypical spermatozoa 

 of different genera. In a comparative study of these peculiarities and 

 differences may be found the explanation of the existence of the dimorphic 

 spermatozoa. Comprehensive work such as this has already been begun; 

 Kuschakewitsch ('ii) has reported briefly upon the first two of a series of 

 forms under investigation by him, and the writer has recently done the 

 same for Stromhus. 



My attention was first called to the question of the dimorphic sper- 

 matozoa in Prosobranchs by Professor E. G. Conklin. At his suggestion 

 Urosalpinx cinerea was made the main object of the investigation, supple- 

 mented by comparisons with the fresh-water snails Goniohasis virginica and 

 Paludina vivipara (the Japanese variety). Material was collected and 

 considerable work was done on these forms. But in May 191 1, while at 

 the temporary laboratory of the Carnegie Institution of Washington 

 established at Port Royal, Jamaica, I was afforded the opportunity of 

 studying and collecting material of various Prosobranchs, including Stromhus 

 bituberculatus. This form proved so interesting and so favorable for research 

 that my immediate attention was centered upon it. My work was further 



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