198 Papers from the Marine Biological Laboratory at Tortugas. 



advanced by another visit, in March 1912, to the temporary laboratory of 



the Carnegie Institution, this time at Montego Bay, Jamaica. Here I was 



able to carry on with partial success some experimental work and also to 



verify in the living cells most of the stages in the development of the apyrene 



spermatozoa that I had traced in preserved material. 



My thanks are due to the Carnegie Institution for the privileges extended 



to me on both occasions, and in particular to Dr. A. G. Mayer, the Director 



of the Department of Marine Biology. Dr. H. A. Pilsbury of the Academy 



of Natural Sciences of Philadelphia very kindly identified the species for me. 



I am under great obligation to Dr. L. R. Cary, of the Department of Biology, 



Princeton University, for turning over to me his sectioned material of the 



testis and oviduct of Goniobasis. Finally, I wish to express a very sincere 



gratitude to Professor Conklin, not only for his many invaluable suggestions 



and criticisms, but also for the keen interest which he has at all times taken 



in the work, 



HISTORICAL. 



In 1837 V. Siebold discovered the fact that there are two kinds of sper- 

 matozoa in the testis of Paltulina vivipara. The typical ones he called hair- 

 shaped and the others worm-shaped spermatozoa. Since then the question 

 of this dimorphism has been investigated by several writers nearly all of 

 whom have given their attention mainly to Paludina. 



Paasch ('43) and Kolliker ('41 and '47) denied the existence of the 

 so-called worm-shaped spermatozoa of v. Siebold, the former interpreting 

 them as being bundles of the hair-shaped spermatozoa and the latter 

 claiming them to be different stages in the development of a single kind of 

 spermatozoon. Leydig ('50), however, not only agreed with v. Siebold as 

 to the existence of a dimorphism in the spermatozoa of Paludina, but also 

 corroborated his description of the development of the worm-shaped kind. 

 His views were very generally accepted until Duval ('80) in\estigated the 

 question. He described an independent origin for the two kinds of sper- 

 matozoa, but in other respects his work was shown by v. Brunn ('84) to be 

 quite inaccurate. 



Although entirely confused in the successions of cell-generations, v. 

 Brunn made a nearer approach to the facts in the case than anyone had 

 done previously. He also described the dimorphic spermatozoa in five 

 genera besides Paludifia and later in the same year extended the entire list 

 to include the following forms: Paludina vivipara, Ampullaria (sp.?), Murex 

 brandaris, M. erinaceus, M. truncidus, Cerithium vidgatum, Nassa mutabilis, 

 Fusus syracusanus, Marsenia (sp.?), Aporrhais pes pelicani, Cassidaria echin- 

 ophora, Dolium galea, Tritonium cutaceum, T. parthenopeum, Vermetus gigas. 



Brock ('87) added to this list by describing the atypical spermatozoa in 

 three exotic Prosobranchs, Pteroceras lambis, Strombus lentiginosus, Cyprcea 

 annulus, C. caput serpentis, and C. lurida. As regards Strombus, his descrip- 

 tions and observations are quite accurate as far as they go, but his figures 

 are lacking in detail. 



