Papers from the Marine Biological Laboratory at Tortugas. 203 



any function with regard to the egg (as is indicated by their presence in 

 the oviduct), that this function can only be of a sex-determining character. 



Lams ('09)^ reported briefly that the development of the atypical sper- 

 matozoa in Murex confirms the description given by Meves for Paludina. 

 In sectioned eggs he was able to find only eupyrene spermatozoa and there- 

 fore came to the conclusion that they alone serve to fertilize the egg. 



The experiments of Kuschakewitsch ('10) have led to some very inter- 

 esting results. By obtaining the ripe eggs of Aporrhais pes pelicani from 

 the oviduct and mixing them with a mass of both kinds of spermatozoa 

 which had been diluted with sea-water, he was able to observe the matura- 

 tion and the first two cleavages of from 10 to 40 per cent of the eggs thus 

 treated. In many instances he could see the formation of an entrance-cone 

 and the entrance of the spermatozoon itself into the egg, but in no case was 

 he able to observe the same processes for the atypical spermatozoa. But 

 in sections of eggs which had been killed 20 minutes after mixing with 

 spermatozoa, he found that the apyrene spermatozoa can and do enter the 

 eggs, either alone or in addition to the eupyrene spermatozoa. Here the 

 apyrene forms undergo a series of degenerative changes and are finally 

 extruded. In later stages, during and after the first maturation spindle, 

 their presence in the egg has never been detected. 



Here it is seen, then, that the apyrene spermatozoa were extruded before 

 any nuclear changes had taken place in the egg. Again, in some Proso- 

 branchs the apyrene spermatozoa are very large and totally immotile, so 

 that one can hardly imagine that they can in any way get into the egg. In 

 view of these facts Kuschakewitsch has come to the conclusion that any sex- 

 determining function in the apyrene spermatozoa is to be doubted. 



Finally, Kuschakewitsch ('11) has briefly described the development of 

 the eupyrene and the apyrene spermatozoa in Conus mediterraneus and of 

 the apyrene spermatozoa in Vermetus gigas. In both cases the development 

 of the apyrene spermatozoa shows many differences from that of the oligo- 

 pyrene of Paludina. All three forms, however, have in common the 

 greatly increased growth of the spermatocytes as the starting-point of the 

 differentiation between the typical and the atypical spermatozoa. 



Kuschakewitsch finds that in Conus no divisions occur in the develop- 

 ment of the apyrene spermatozoa and that the spermatocyte is transformed 

 into the spermatozoon by the disappearance of all the nuclear material 

 and the subsequent growth of two fibers and two flagella from the centrioles. 

 The nucleus may either gradually dissolve as a whole or it may fragment. 

 The process of fragmentation may take place in either of two ways: the 

 nucleus may become vesiculated and then break down into two and later 

 into several compact and vacuolated spheres, or it may become compact 

 and break down into a number of dense chromatic bodies which probably 

 represent chromosomes. In either case the end result is the disappearance 

 of all the chromatin. The two fibers eventually come to lie at the surface 



> I have been unable to obtain this publication and have therefore relied upon the review of it given by 

 Kuschakewitsch. 



