204 Papers from the Marine Biological Laboratory at Tortugas. 



of the cell and the flagella with the pair of centrioles belonging to them at 

 one of the ends of the spermatozoon. The conduct of the mitochondria 

 is very striking; they appear first as granules, but eventually form fibers. 

 During the course of development one or more vacuoles appear in the cell, 

 which are quite characteristic of the adult spermatozoon. 



In Vermetus, too, he finds that there is a direct breaking down of the 

 nucleus of the spermatocyte. The chromatin forms into karyomerites and 

 upon the dissolution of the nuclear membrane these lie free in the cytoplasm 

 and are all gradually absorbed. In the spermatocyte there is to be seen a 

 pair of centrioles lying in a thicker mass of cytoplasm ; these form a group of 

 secondary centrioles at one pole of the cell at the time of the dissolution of 

 the nuclear membrane or immediately afterwards. The secondary centri- 

 oles give rise to a number of threads which eventually form a bundle of 

 axial fibers whose middle portion passes through the center of the cell and 

 whose ends extend beyond it in either direction. In the cytoplasm of the 

 cell chere arise a great number of thick- walled chambers whose cavities are 

 filled with a clear substance. In each of these chambers a sphere of albumen 

 is gradually formed. In the spheres themselves there appears either a large 

 central vacuole or several smaller peripheral ones. Afterwards the contents 

 of these vacuoles seem to become greatly condensed. 



In his conclusions Kuschakewitsch points out the fact that the develop- 

 ment of the atypical spermatozoa in Conns and Vermetus does not present 

 the same parallel to the development of the typical spermatozoa as Meves 

 established in the case of Paludina. He thinks, however, that we are justi- 

 fied in speaking of these structures as "spermatozoa" when the fact is borne 

 in mind that their origin is the same as that of the oligopyrene spermatozoa 

 of Paludina and Miirex and that it is hardly conceivable that, in the well- 

 defined group of Prosobranchs, structures with a similar origin would have a 

 different morphological significance in different members of that group. 

 Thus the mode of the development of the apyrene spermatozoa in Conns 

 and Vermetus can in no wise be regarded as supporting the hypothesis of 

 V. Brumm, that these structures are rudimentary ova. On the contrary, in 

 Conns true eggs appear in the testis in addition to the apyrene spermatozoa.^ 



As regards Stromhus the writer has shown (Reinke '12) that here, too, 

 the development of the apyrene spermatozoa takes place without any 

 maturation divisions, and furthermore that there are no processes, such as 

 the formation of chromosomes and abortive spindles, which could be 

 described as surviving from a condition in which those divisions did take 

 place. In addition there is the fact (which will be shown in the succeeding 

 pages) that the apyrene spermatozoa are not derived from the spermato- 

 gonia. But in spite of these facts, there are good reasons for still applying 

 the term "apyrene (oligopyrene) spermatozoa" to these structures. In the 

 first place, the name is well established and has been used commonly, and 



Since the above was written there has appeared another paper by Kuschakewitsch giving a detailed 

 account of the development of the eupyrene and apyrene spermatozoa in Conus and Vermetus. In it he states 

 that the apyrene spermatocyte of Conus sometimes undergoes a division after the nucleus has disappeared. 



