STAINING-REACTIONS OF THE GEKM-XUCLEI 1 75 



Webber and Ikeno have produced apparently strong evidence ^ that 

 they arise separately and dc 7iovo in the cytoplasm. After the ensu- 

 ing division (by which the two spermatids are formed) the astral rays 

 disappear, and the blepharoplast gives rise by a peculiar process to a 

 long, spiral, deeply staining band, from which the cilia grow forth. 

 The later studies of Shaw ('98, i) and Belajeff ('99) on the blepharo- 

 plasts in Onoclca and Marsilia leave no tloubt that these bodies are 

 to be identified with centrosomes. In Marsilia Shaw first found the 

 blepharoplasts lying at the poles of the spindle during the anaphase 

 of the first maturation-division and very closely resembling centro- 

 somes. Each blepharoplast, at first single, divides into two during the 

 late telophase, and during the prophases of the second division the 

 halves diverge to opposite poles of the nucleus and lie at the respec- 

 tive spindle-poles. This account is confirmed by Belajeff, who shows 

 further that during the prophases astral rays surround the blepharo- 

 plasts, and a central spindle is formed between them (Fig. 88). 

 Belajeff also finds centrosomes in all of the earlier spermatogenic 

 divisions. The blepharoplasts are thus proved to be, in one case at 

 least, dividing organs which in every way correspond to the centro- 

 somes of the animal spermatocytes ; and the justice of Belajeff's 

 comparison is demonstrated. Shaw believed that the primary blepha- 

 roplast, which by division gives rise to those of the two spermatids, 

 arose de novo. He made, however, the significant observation that 

 in Marsilia "blepharoplastoids," exactly like the blepharoplasts, ap- 

 pear at the spindle-poles of the preceding (antepenultimate) division, 

 and that each of these divides into two in the late telophase. These 

 are said to disappear, without relation to the blepharoplasts which at 

 a slightly later period are found at the spindle-poles of the first matu- 

 ration division ; but in view of the demonstrated continuity of the 

 blepharoplasts during the second division we may well hesitate to 

 accept this result, as well as Webber's conclusion regarding the 

 independent and separate origin of the blepharoplasts in Zamia. In 

 any case the facts give the strongest ground for the conclusion that 

 the formation of the spermatozoids agrees in its essential features 

 with that of the spermatozoa, and for the expectation that the history 

 of the achromatic structures in fertilization will yet be found to show 

 an essential agreement in plants and animals. 



E. Staining-reactions of the Germ-nuclei 



It was pointed out by Ryder in 1883 that in the oyster the germ- 

 nuclei stain differently in the two sexes ; for if the hermaphrodite 



^ Dr. Webber has kindly given me an opportunity to look through his beautiful prepa- 

 rations. 



