PTERIDOPHYTA. 



Belajeff ('98). Prior to the division of the grandmother-cell of the 

 spermatozoid, /. e., the last cell-division in the spermogenous tissue 

 of the antheridium, which gives rise to the cells that develop directly 

 into the spermatozoids, there appears on opposite sides of the nucleus 

 a small globular body of a homogeneous structure, staining rather 

 densely (Fig. 51, A). These bodies are not provided with any radia- 

 tions. In Onoclea there is, immediately surrounding the nucleus, a 

 region of less granular cytoplasm from which, undoubtedly, the weft 

 of spindle fibers is developed. These bodies, which are the primordia 

 of the blepharoplasts, lie just at the outer edge of this region or weft 

 (Fig. 51, A). In the telophase a blepharoplast primordium lies near 

 the depression of each daughter-nucleus, very near the pole of the 

 spindle (Fig. 51, B, C). Each appears now to be a hollow globular 

 vesicle. Soon after cell-division is completed the development of the 

 daughter-cells directly into spermatozoids begins. The blepharoplast 

 primordium becomes somewhat lens- or crescent-shape in Gymno- 

 gramme, with the concave side turned toward the nucleus. The 

 nucleus at the same time becomes flattened upon one side and gradu- 

 ally passes into a crescent- or pear-shaped body (Fig. 51, D, E). The 

 blepharoplast has elongated into a thread or band, which follows the 

 convex side of the nucleus and is rather close to it. One end of the band 

 now extends beyond that end of the nucleus \vhich will be anterior in 

 the mature spermatozoid (Fig. 51, F, G). With further development 

 the blepharoplast moves away from the nucleus to a position just 

 beneath the plasma membrane (Fig. 51, H). At this stage the cyto- 

 plasm in Onoclea (Shaw, '98) shows a depression corresponding to the 

 concave side of the nucleus. At about this period in the development 

 in Gymnogramme, according to Belajeff, the cilia make their appear- 

 ance as outgrowths of the blepharoplast. The nucleus elongates, 

 becoming more slender, and gradually assuming a spiral or corkscrew 

 shape of two or three turns. In the mature spermatozoid (Fig. 52, 

 A) the nucleus is thicker, tapering abruptly, and sometimes to a point, 

 at the posterior end, but gradually forward into a slender anterior end. 

 It is oval in cross section, or, in some cases, slightly flattened on the 

 inner side, especially in the thicker posterior part. In mature sperma- 

 tozoids of Onoclea struthiopteris, fixed and stained on the slide, the 

 cytoplasmic part seems to be in the form of a band which conforms to 

 the spiral course of the nucleus. It is broadest at the anterior end, 

 which extends a short distance, about one or two turns, beyond the 

 anterior end of the nucleus, but it narrows gradually backward, dis- 

 appearing at a point which marks the thickest part of the nucleus 



