Papers from the Marine Biological Laboratory at Tortugas. 199 



There then followed two papers, one by Kohler ('89) on Murex, and the 

 other by Auerbach ('96) on Pahidina. These authors estabHshed the 

 fact that there is an almost complete loss of chromatin during the develop- 

 ment of the worm-shaped spermatozoa, but they too were unable suc- 

 cessfully to trace the succession of cell-generations and thus they made 

 little or no material advance over the work of v. Brunn. To these obser- 

 vations Erlanger ('97) added a minute description of the adult worm- 

 shaped spermatozoon in Paludina. 



It is unnecessary here to go into a detailed discussion of the literature 

 mentioned above, as it has all been discussed in the work of Meves ('03). 

 This author has given a detailed and correct description of all the various 

 stages in the development of both kinds of spermatozoa in Paludina. 

 Furthermore, he has given careful consideration to the findings of the more 

 important of the earlier writers and has shown wherein they were in error. 



Meves describes the earliest differentiation between the two kinds of 

 spermatozoa as occurring during the growth period of the spermatocytes, 

 the spermatogonia of both being alike. He denies the statement of v. 

 Brunn that the basal nuclei reproduce by direct division. This seems to 

 the writer to be a debatable ground and forms the only weak point in 

 the work of Meves. v. Brunn, of course, was quite wrong in supposing 

 that the cells formed by this direct division of the basal nuclei give rise 

 eventually to both kinds of spermatozoa; he failed to recognize the sper- 

 matogonia as distinct primitive elements of the testis. According to 

 Meves these cells undergo unequal growth and thus give rise to both the 

 hair-shaped and the worm-shaped spermatozoa. At the suggestion of 

 Waldeyer he uses the terms eupyrene and oligopyrene to describe the two 

 kinds of spermatozoa. The words have reference to their adult condition, 

 i. e., those provided with the ordinary amount of nuclear material and 

 those with but a little; similarly, apyrene spermatozoa are those in which 

 the entire nucleus disappears. 



According to Meves, the oligopyrene spermatocytes of Pahidina grow 

 very much larger than the eupyrene and are clearly distinguishable, not 

 only on account of their increased size, but also on account of their peculiar 

 pattern and the presence of a large centriole and sphere. Preparatory to 

 cell-division, this centriole divides and a little later both halves fragment 

 into many smaller centrioles. The division which now occurs is abnormal. 

 Two groups of very small centrioles form the poles of an ill-defined spindle. 

 The daughter chromosomes pass to both poles, but before the division of 

 the cell-body is completed the majority of them scatter again throughout 

 the cytoplasm; four of the chromosomes, however, remain at the poles to 

 form the new nuclei. These become vesiculated and may all unite with 

 one another or some may unite and others remain single or all may remain 

 single. Thus there may be four, three, two or only one nuclear vesicle in 

 the secondary spermatocyte. The remaining ten chromosomes undergo a 

 peculiar vesiculation in that the chromatin becomes lumped as a crescent 

 on one side of the vesicle. 



