XIII 



EQUISETINE^ 



427 



it thus remains single-layered, as in Maratiia and OsutiDida. 

 There is often a triangular opercular cell (Fig. 221, D, 0), re- 

 calling the similar cell in these forms. 



Development of tJic Spennatozoids 



The large size of the spermatozoids of Equisetinn makes 

 them especially suitable for the study of their development, and 

 this was traced with some care in E. telinateia. The material 



Fig. 222. — Development of the spermatozoids, X looo. A, Three of the central cells of an antheridunn 

 before the final division; B-E, final nuclear divisions in the sperm cells; F-J, development of 

 the spermatozoid from the nucleus of the sperm cell ; c, the cilia ; K, two free spermatozoids ; r', 

 the vesicle. 



used was fixed with i per cent chromic acid, stained with alum- 

 cochineal, and microtome sections were then examined in Canada 

 balsam. The nuclei of the sperm cells previous to their final 

 division are globular and show one, sometimes two, small but dis- 

 tinct nucleoli, and numerous chromosomes. In exceptional cases 

 the two " directive spheres " could also be seen. Previous to 

 the final division the latter take their place on opposite sides of 

 the now somewhat flattened nucleus, whose nucleolus cannot be 

 distinguished and whose nuclear segments are very distinct, 



